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DTM -151-S Manual

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3. ACUSTA Du uddy 5170 JW SCSHW 332M 9 0 ZT XOOT 42845 330M v O 9 j u 9 1 O OONZT AOASTSSA 92 T ZAT 5 j u 9 T 00306 AOASTSEA 2 5 338 p O FS GUT AOASTSOA UW 40445 339 970 35 HOT 4O4sISe2 JW SZAJS 339 7 0 SG BAT JW 9364415 330 0 G AOASTSST UTTJ FROM 92 FT XOCC JO4STS I JW SZAJS 336 0 G AT JW SCSUN 338 9 O 31 AOOT 4O3STS9A3 UTTJ SzSWW M9 O 31 0302 AOASTSSA 92 ST 3005 UTTJ 5 M9 0 T OXOZ UTF 92 T 9Xt 5 5 SCSHN 748M 9 0 FT 1 lt 5 336 40 ST 0 203515 AW GCH IS 332M p O 85 HOT 439 9 ZT OOXc AOASTSEA AW 40845 338 7 0 SS AT qod 9 od 34 v 9vOSN dis wug azedun 3exoos 5 4
4. GCSHW SC ST 2615 T 0L AW SCSNW 43 9 0 T THS T LY uor3draoseq 430 TST WLA 55 QHVOH SLoOnGONd LNHSWAXNOSVIW SIT SLuVd GULINIT ASOTIONHOGL 4 5 13 DTM 151 serial User s Manual 5 14 DTM 151 serial User s Manual GROUP 3 TECHNOLOGY LTD LIMITED WARRANTY Group3 Technology Ltd hereinafter called the Company warrants instruments and other products of its manufacture to be free from defects in materials and workmanship that adversely affect the product s normal functioning under normal use and service for a period of one year from the date of shipment to the purchaser The obligation of this warranty shall be limited to repairing or replacing at the discretion of the Company and without charge any equipment which the Company agrees is defective as set out above within its warranty period The Company will reimburse lowest freight rate two way charges on any item returned to the Company s factory or any authorized distributor or service center provided that prior written authorization for such return has been given by the Company This warranty shall not apply to any equipment which the Company determines to have become defective owing to mishandling improper installation alteration negligence inadequate maintenance incorrect use exposure to environme
5. 60000089 5 dis Aem 12000089 TTJO4d FAOS 2 90000679 ANOT 10000179 deo oTU3TTOUOU JULY uoradraosed v 55 TIVH Tn 8 4 4a sa va T 4 T 242 T M v vac T 22 T To AAO WSooozost SLOndONd LNHSWSH SVHIW OLLANOVA 1511 SLUVd GHLIWIT ADSOTIONHOHd t 5 5 DTM 151 serial User s Manual 2402 133 5 92 3198 JO T L33HS 1 310 100 N 991900051 33 Tef ino N 5 hoor 991900051 33 oa ges dyoga 405532044 191335 fedl oF py plete 14904 405542044 91435 2 MSN 2 GNYDIONY Ten ONUTU3Z 2 QNUTDOnU NUS3SOM 12 Od 1 NI 24983503 X08 Od END 30802241 Xu 7 g z Q11 A9010NHO31 40039 NI aZ sz 41094481 ST MOIS YT A90710NHO31 EdNOY9 122 A TA 8 ZA oy ss0 TT a soot et 37 sete 8n sn 839 2 T S 5901 8 4 8 o
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9. 1 in 600 000 of bipolar span as shown on front panel display range display resolution _serial GPIB resolution gauss tesla gauss tesla 0 3 tesla 0 01 0 000001 0 001 0 0000001 0 6 tesla 0 02 0 000002 0 01 0 000001 1 2 tesla 0 04 0 000004 0 01 0 000001 3 0 tesla 0 1 0 00001 0 01 0 000001 DC mode with digital filtering OFF and AC mode 1 in 120 000 of bipolar full scale span in display range display resolution _serial GPIB resolution gauss tesla gauss tesla 0 3 tesla 0 05 0 000005 0 001 0 0000001 0 6 tesla 0 1 0 00001 0 01 0 000001 1 2 tesla 0 2 0 00002 0 01 0 000001 3 0 tesla 0 5 0 00005 0 01 0 000001 20 bit digitizing of field reading DTM 151 with LPT 141 or MPT 141 probe 0 01 of reading 0 006 of full scale max at 25 C DTM 151 with LPT 141 or MPT 141 probe calibration 10 ppm of reading C max zero drift 1 microtesla 0 0003 of full scale C max add 3ppm C for each meter of probe cable 0 1 max over 1 year DTM 151 serial User s Manual 2 1 Response time Peak hold mode AC mode Display Indicators Display modes Digital filtering Keys Digital interfacing Digital data format Commands Output responses 2 2 10 measurements per second Full scale change of displayed field reading settles to within resolution in less than 0 3 second filtering off see below Displays maximum field since mode entered or reset Peak hold is im
10. Display mode hold teslameter display shows peak dc or ac field Display mode normal teslameter display shows current field value Display mode temperature teslameter display shows temperature Offset calls up offset mode and enters offset which is added to all field readings Default 0 n in range 79999 9 to 79999 9 The one offset applies to all ranges Peak hold field requests a peak field reading from the teslameter Test teslameter front panel display Range selection selects 0 3 tesla range Range selection selects 0 6 tesla range Range selection selects 1 2 tesla range Range selection selects 3 0 tesla range DTM 151 serial User s Manual SCn SEO SE1 SFn SLn SMO SM1 01 00 STn SUO SU1 SWAn SWEn SWZn SZn UFG UFT WA WE WZ Yn CTRL B CTRL D CTRL U CTRL X Set calibrate enters calibration factor n for the selected range like Cn but enters factor not desired field reading Default n 1 Turn OFF echo of every character received Turn ON echo of every character received Default set by S2 4 Put in a simulated field to replace the measured reading X cancels Set scale enters scale factor n for all ranges like Ln but enters factor not desired field reading Default n 1 Send mode field readings sent when requested by F command only Send mode field readings sent at intervals defined by Kn command Default for address 0 S1 1 to S1 5 OFF set by S2 1
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12. remove the 3 fixing screws to release the cover Use 3 conductor power cord For safety from electrical shock it is essential to provide a reliable ground connection to the DTM case Make sure the ground wire is connected as shown in Fig 1 Strip about 60 mm 2 5 in of outer jacket from the cord and strip 5 mm 3 16 inch of insulation from the 3 wires Pass the cord through the grommetted hole in the cover Loosen the screw securing the cable clamp and pass the cord through the clamp Tighten the clamp on the outer jacket Terminate the wires and fit links according to the supply voltage as set out in Fig 1 below Replace the orange cover making sure that wires are not pinched in the process For safety reasons do not operate the unit with the cover off Note that input power protection is provided by a thermal fuse wound into the power transformer This fuse will open in the event of transformer overheating rather than on excess current The power input must be connected as shown to include the thermal fuse in the circuit correctly If a fault causes transformer overheating and subsequently the fuse opens the transformer must be replaced with the genuine Group3 part PWR 115V 208V 230V Fig 1 Power Input Connections of the L option DTM 151 serial User s Manual 3 3 If desired the wiring may be protected by installing an external fuse in the ac power feed Suggested fuse ratings are 200 mA for 115 volts or 100 mA for 208 and
13. 230 volt operation When the unit is first powered up the display shows Group 3 for 2 seconds before field measurements appear If the Hall probe is not plugged in the field reading display is replaced with noProbE 3 4 FIBER OPTIC CONNECTIONS The DTM 151 _S has facilities for communicating with external devices such as computers or terminals using its serial I O ports The teslameter may also be set up to relay communications through other compatible Group3 devices using the Group3 Communication Loop See section 4 5 There are 3 bi directional ports 2 using standard RS 232C signals the third employing fiber optics In electrically noisy environments or where ground loops could be troublesome or if a voltage gradient must be traversed it is advisable to use fiber optics for the serial data link The teslameter s fiber optic ports accept Hewlett Packard HFBR 3500 series fiber optic cables up to 60 meters in length Fiber optic cables are fitted with a blue connector one end and a gray connector at the other Although functionally identical the colors make it easier to keep track of cable routing when connecting up a system The convention is to use gray at send ports and blue at receive ports To connect the cables simply push the connector in through the appropriately labelled hole in the teslameter s rear panel The connector will snap into place To disconnect give the cable a gentle tug Inspect the cable ends to ensure the inn
14. 70000579 S0000179 70000579 90000579 50000579 90000599 60000579 60000579 90000579 80000 9 20000011 TOOOOOTT deo AULP T 9 2 WUc z xurx deo ouou Z 29 19 2 peeq 4801 T 09 2 lt pezr e3eu AUEE T 92 xurx deo ouou 48170 68 48 2 ANOT T 96 2 Wucg z xurx deo AOS T SS 2 ANOT T TG D uug z JUOT T 2 wug Z 4 T 082 JUOT 52 deo JUL Z 69 89 2 JUOT LY 2 deo pezr e3eu 4 0 T 9y deo pezr e3eu ANT T Sv AGE ANT v uug z AUT Eb 2 peeq AGE ANT T deo JUL T Tb D OdN 41 2 0v 2 deo xe4
15. DTM 151 serial User s Manual vector enters this side of the probe The target represents the tail of the vector arrow Magnetic field convention is that field lines are directed from N pole to an S pole Fig 8 gives the dimensions of the two styles of probe and shows the position of the most sensitive point If the exact direction of the magnetic field is unknown its magnitude be measured by putting the DTM in the peak hold mode and slowly rotating the probe As the probe turns and the measured field rises and falls its maximum value is held on the display See section 4 4 2 page 4 4 LPT 141 and LPT 231 ceramic reference surface sensitive aluminium cap area 4 5 dia nom 5 0 dia nom 4 2 41 0 1 0 20 1 8 5 1 0 2 2 5 20 13 14 0 30 2 1 0 0 2 main cable rigid cable junction flexible wires all dimensions in mm target error 0 3mm angular error in transverse plane 1 seating error on ceramic 0 4 max MPT 141 and MPT 231 reference surface 5 0 dia 3 2 dia nom _ 14 0 0 2 ceramic Lap ay AV AVAVAVAVAVAVAVAVAVAVAVAVAVAVAV sensitive area 3 x 4030 1 8 5 0 Uy main cable 20 nom 50 2 exposed ceramic area 1 5 10 2 4 5 dia nom cable junction flexible wires 0 3 wide min 2 0 nom sensitive area is on centerline of epoxy 40 2 0 62 0 02 all dimensions in mm angular
16. I1 JW SZAJS 338 7 0 85 4065 T ET 4 88000089 Zo4stsed JW SZAJS 338 O 85 ENE T 92000099 92445 33 0 86 T Ita 59000069 4O4SISeJ JW GCN4S 7 0 G T ot a avg qod paeoq T Tod 07000189 zxz em y T 84 ZTOOOTS9 sutd 9xz T Ld TT000189 34ubrea34s surd 9 9d 70000189 Aem ve 0000189 0S 9T089 od T vd 20000789 od 31 9 2 d 12000189 prob EXT TOOOOTS9 sutd Aem 97 0000G29 aueaano ubru Ed 10000449 OSStZZ SGASS OTESSA I TII T 70000549 28146 020 2269 PTOAOL T 61000089 uuo aedun L 6 amp 0000089 em Ov TL 90000089 Aepros JI Aem gz 9r 50000089 5 2 5 edi 2 ZeG 70000089 OI edtm 9 9 9xv 0000089 4 enp T Tee 20000089 3exoos edtm 8
17. MSN 2 ONU DIOnV XNUS3SON 12 8 Od 017 ASOTONHOSL 21 EZY 421 mezt 3ner STO R t lt ANZZ ANGET AN T 4 9 ZE zzo ezn pz 0 ern zT eL 21 N9 asn ONT TT 8 9215 6 6101 35 AT e A 9 Lu 02858404 220 r ANLb L XT Tra LEI Te 62 99 AS TTO 34 ero T S L TIHbL L TIHPL 35 ZH 6 92 60 80 20 90 so vo 0 20 TO 2 8 EST 20 stn 1 TAL S MONT OQ AG o DTM 151 serial User s Manual b 40 133 5 NON 8Z 3190 2001021 1 44908 141 114 b JO 133 5 82 3194 2 2 ONYTAONY ANYVG3SOY 12 Od 017 A 07ONH23L 001021 2jILUH3HOS 034904 901UNU 181 110 HOZZ INTL 293 pro ON 1 3Z2 2 4 TTT T Od 017 ASOTONHOSL 40039 2 s
18. RX 3 receive data output TX 4 request to send input DCD or open 5 clear to send output 5v or pin 4 6 data set ready output RTS or 5V 7 common circuit common 8 carrier detect output RTS or 5V 20 data terminal ready input CTS or open option according to requirements of external equipment Note connect CTS and DCD to 5 volts if not otherwise used Table 3 RS 232C Connector Pin Assignments Modem Mode DTM 151 serial User s Manual 3 7 Pome M M M unit T T a b Fig 3 Send and Receive Jumpers a Modem Mode b Terminal Mode M m pin location The option 1 and 2 jumpers configure the relationship between the RS 232C connector and the ports For single device systems option 2 should be selected Refer to Fig 4 below Section 4 5 describes the use of the option jumpers in setting up the alternative G3CL arrangements B H rear 4 of 1 m pin location unit E UN a b Fig 4 Option Jumpers a Option 1 b Option 2 2 1 a Fig 2 also indicates the positions of the wire wrap posts on which appear the RTS CTS and DCD signals 5 volts and ground and posts which connect to RS 232C connector pins 4 5 6 8 and 20 These pins may be wire wrapped according to the options set out in Tables 2 and 3 When pins are adjacent they may be connected more easily with push on jumpers 3 6 INTERNAL DIP SWITCH SETTINGS The Processor Board in the DTM is provided with t
19. T AG dOYSOT8LDN T bz n 314 02 NVEtOZZLGV T tc n snq 8X9S7C 42 022858424 T ec n due do A 21 03 03 52150 020 duedo 4 AG Z T A T ST A dots ATIJ A C Tenp NLOTLOHPL T T A ANYN 3ndut z penb T ET A 5 TI A T N 98EWI T duedo esrou o uorsroead T Ta 6120 81 5 JUTOd 3593 Z uang uuo 002 002 T 20351592 33 9 FT 004 T 6 d JW SCAHA4AS 7348M 7 0 3 C 28 18 381591 g u 33e 92 0 1 0 38 T 08 UTTJ T T 8 4 l1 0 2949 T 64 3srsea j u 4270 8170 2 8 T 82 4 j u 92 8100 2978 LL 4 18 5 92 SCHIS 339 v O 38 HOT T 74 5 AW 92445 332M 7 0 6 X9G T ez a 5 338M F O 9 AZZ T L JW SZAJS 33 0 8546 XO9S T TL
20. Zoystsez 1 0 339 9 8862 J W 339 9 8170 OTE 66 94 od 4 5 5 2 peeq AST INOT deo oy TOUW JULY KIGWASSV WOUdd SOWO 8 X AS 79046 GR ee V 0 NN NN VUhhA M paeoq qexyoos dis a ddd NNd e ddd e d a 4 430 SoondOWd LNAWHYNSVYEW OLLYNOWN 1611 SLINVd GHLIWIT dnowd SANI m EYO pue 240 LHD eseo siy U s eje1 si pJeoq 5141 20000 19 SOWO 314 8 X AB 9042 00000149 UTTJ 33 GC 51 02600159 5 AN SCSNN 2384 9 0 ST 81000249 J W D uddgT 9 1 0 00000299 j u 9 842 81000269 j u 339 9 8 00000249 444 339 9 84627 paeoq 10000 89 OTE 66 94 od Aem oz 20000289
21. as described in sections 3 2 and 3 3 Allow 30 minutes for the instrument and probe to stabilize For absolute zeroing place the probe ina zero field region either in a zero field chamber or inside a suitable magnetic shield so that the probe is shielded from the earth s magnetic field and other stray fields If desired a relative zero setting may be done the instrument is zeroed after the probe is placed in its measurement position Thus any ambient field is automatically subtracted from subsequent measurements The probe should not be moved once zeroing is complete About 5 of full scale may be zeroed out without reducing full scale span below specification The zero field reading is affected slightly by the presence of metal against the probe s back surface If the probe is to be used clamped to a metal surface or in a probe holder it should be zeroed in the same situation Allow the probe to stabilize thermally for a minute or two before zeroing A range is selected by pressing the RANGE key The four range indicators show the selected range The RANGE key selects the ranges in turn in the sequence 0 3 0 6 1 2 and 3 0 tesla If a single range probe is in use the RANGE key will have no effect The zeroing process is implemented by pressing and releasing both keys together Alternatively press and hold either key while pressing the other key twice momentarily The display will read ZEro for a moment indicating that zeroing has occ
22. can be set using the Y command See page 4 11 The value entered is the half window on either side of the current field reading The default value on system reset is 1 gauss for a total window width of 2 gauss independent of range The digital filter takes the field readings before processing by zero calibrate offset and scale functions and filters the values by performing the following computation F new F old F F old J where F old is the previous field reading display F new is the updated field reading display F is the most recent unfiltered field reading J is the filter factor The effective time constant of the filter is dependent upon both the rate at which field measurements are made and the value of J according to the formula T P In u J 1 where Tis the filter time constant P is the period between field measurements Field measurements are made ata fixed rate of 10 per second so P 0 1 A default value of 41 for J is effective when the DTM is reset with the CTRL X command or S2 8 This gives an effective time constant of 4 seconds The filter time constant may be changed by entering a new value of J using the Jn command See page 4 10 4 14 DTM 151 serial User s Manual 4 7 TRIGGERED OPERATION Triggering allows one or more teslameters to make synchronized field measurements on demand The teslameter is set for triggered operation by entering the command GV To initialize a measurement ente
23. command is transmitted Usually echo is set ON if the 26 way RS 232C port is used and OFF when using either pair of G3CL ports If echo is ON in the latter case the teslameter will transmit each input command twice first the original command rippling through then the echoed command When echo is OFF when the RS 232C port is used the input command will not be returned to the external control device 52 6 when ON adds the field and temperature units characters T or and C to the transmitted string after the numerical values 3 10 DTM 151 serial User s Manual 52 5 7 affect the operating mode of the teslameter 52 5 selects the field units gauss or tesla used by the device S2 7 invokes digital filtering of the field reading S2 8 allows the user to reload default settings where all the numerical values entered by the operator are returned to their default values and switch selectable functions are instated as set on the switches To load defaults switch S2 8 ON wait 1 second then switch OFF again If the switch is left ON defaults will be loaded each time the teslameter is powered up The display shows the message rESEt each time defaults are loaded When defaults are loaded on power up the rESEt message follows the Group3 power up message The functions controlled by S2 1 through S2 7 can also be changed remotely by serial input commands as set out in section 4 5 To revert to switch control change the switch setting wait 1 seco
24. filtering S2 8 defaults no action defaults loaded Table 4 DIP Switch Functions DTM 151 serial User s Manual 3 9 51 8 51 7 51 6 data bits parity stop bits OFF 7 2 OFF OFF 7 odd 2 OFF ON OFF 7 even 1 OFF ON ON 7 odd 1 ON OFF OFF 8 none 2 ON OFF ON 8 none 1 ON ON OFF 8 even 1 ON ON ON 8 odd 1 Table 5 Serial Data Format Switch Settings The switches are read by the processor once per second so the effects of changed settings can be observed in real time If the system contains only one device it is recommended that its address be set at 0 S1 1 through S1 5 OFF Then the external control device does not need to initiate commands with a device address command Also in a single device system S2 1 can be set ON so the DTM will transmit field readings continuously at the maximum rate of 10 per second without first being addressed S2 2 selects the character sent as string terminator S2 3 when ON introduces a pre terminator character before the final string terminator The pre terminator is the character not selected by S2 2 The terminator sequence as selected by S2 2 3 is as follows 52 2 If cr S2 3 ON cr If If cr Table 6 String Terminator Switch Settings 52 4 controls the echoing of input commands by the teslameter If echoing is selected every command from the external control device is echoed before the response to the
25. in this case Table 2 below gives the pin assignments and signal names when the teslameter is configured as a Data Terminal Equipment DTE This will be referred to as terminal mode 3 6 DTM 151 serial User s Manual The unit can also be set to behave like a Data Communications Equipment DCE for example a modem The instrument is then said to be in modem mode See the RS 232C connector pin assignments for modem mode below in Table 3 Fig 2 shows the location of the RS 232C pin field moveable jumpers and wire wrap posts on the Processor Board For terminal mode the send and receive T M jumpers should be pushed onto the square posts lined up parallel with the long side of the circuit board In modem mode the jumpers are set at right angles to the above See Fig 3 RS 232C signal connection in signal name direction DTM 1 protective ground instrument case 2 transmit data output TX 3 receive data input RX 4 request to send output RTS or 5V 5 clear to send input CTS or open 6 data set ready input DCD or open 7 circuit 8 carrier detect input DCD or open 20 data terminal ready output option according to requirements of external equipment Note connect CTS and DCD to 5 volts if not otherwise used Table 2 RS 232C Connector Pin Assignments Terminal Mode RS 232C signal connection in pin signal name direction DTM 1 protective ground instrument case 2 transmit data input
26. option are supplied with a plug pack Connect the plug pack to a convenient ac power source first checking the voltage marked on the plug pack and insert the cable connector into the power receptacle on the DTM rear panel Instead of the plug pack the unit can be powered by any convenient source of ac or dc either polarity 9 to 15 volts capable of supplying 0 7A rms ac or 0 5A dc The cable connector required for power connection to the DTM is a standard coaxial plugpack connector with 2 1mm centre hole and is generally available from electronics suppliers For extra immunity to damage and operational disturbance caused by serious high voltage sparking near the teslameter the use of the Group3 model PS12D7 off line switch mode power supply and the Groups ferrite kit part no 11000036 is 3 2 DTM 151 serial User s Manual recommended These accessories will greatly reduce the amount of electrical transient energy entering the teslameter The ferrite kit includes a suppressor which fits to the probe cable near the point of entry to the teslameter to reduce the effects of transients picked up on the probe cable For a full discussion of techniques to promote trouble free operation in electrically noisy environments see section 3 12 of this manual Powering the L option teslameter The L option will accept power input from the ac power line Access to the power input terminals of the L option is obtained by taking off the orange cover
27. protected from any chance of receiving a direct hit by ahigh voltage discharge The probe should have shielded cable if the meter is to be used in an electrically noisy environment The cable shield is RFI screen not a high current path so if there is any possibility of an arcing discharge hitting the probe area then the probe head and part or all of the cable must be enclosed in a metal tube non magnetic near the probe head or shielded in some other way The probe cable should be routed away from any power high current or high voltage wiring It should be shielded from any capacitively coupled noise effects If the cable runs close to any section of the apparatus that could be subjected to a very rapid change of potential when a spark discharge occurs then the probe cable may need additional shielding to prevent capacitive coupling of the noise The retaining jack screws designed to hold the probe connector onto the teslameter must be screwed up finger tight as they form part of the electrical connection of the shield system The woven braid of the probe cable is terminated to the probe connector case The retaining screws then connect the probe connector case to the teslameter case The teslameter itself should be sited in a sheltered location where it will not be exposed to spark discharges or radiated or capacitively coupled noise The teslameter case is made of metal for shielding reasons However of necessity itis less than perf
28. standard Amphenol 57 20240 with metric standoffs DTM 151 serial User s Manual 2 3 Power source Enclosure Ambient field Temperature range Instrument weight Probes user entered data storage for 30 days with power off ac min 8V at 0 7Arms max 15V at 0 4Arms dc min 9V at 0 5A max 19V at 0 25A ac line input plugpack supplied Power fuse on processor board 1 amp antisurge 5 x 20mm To obtain maximum spark protection use PS12D7 power supply and ferrite kit 11000036 See section 3 12 L option 115 208 230 V ac power input aluminum 217 x 125 x 50 mm textured finish light tan color tilt stand fitted to bench models Maximum operating field for instrument 10 millitesla with single range probe 0 5 millitesla with multi range probe 0 to 50 operating absolute maximum temperature of probe 60 1 2 shipping weight 2 5 kg LPT series transverse types sensitive area 4 1 6mm probe head size LPT 141 and LPT 231 14 x 14 x 2 5 mm MPT series miniature transverse types sensitive area 1 0 x 0 5mm probe head size 132 230 MPT 141 MPT 231 14x 5x 2mm Standard cable length 2 meters Special cable lengths to 30 meters Probe cable is shielded DTM 151 serial User s Manual ORDER CODES Basic teslameters capable of four measurement ranges 0 3 0 6 1 2 3 0 tesla full scale support all LPT and MPT series probes plugpack suppli
29. teslameter contains a fifo buffer which can accept more than 30 command characters in an unbroken stream PARITY ERROR a mismatch in parity in one or more characters received DATA CARRIER NOT PRESENT handshake pin 4 DCD has gone low commands cannot be accepted in this state See Fig 2 on page 3 6 FIXED RANGE PROBE an attempt was made to change the range with a single range probe connected to the teslameter NO PROBE a field reading was requested when a probe was not connected OVERFLOW the computed field value was outside the range 199999 9 OVER RANGE the current field being measured is too high for the selected range 4 12 DTM 151 serial User s Manual 4 5 4 Some Examples Using the Commands With the teslameter connected to a source of serial data as described in Sections 3 4 and 3 5 send the character Z to the teslameter This will zero the range currently selected To check which range is current send IR to the teslameter The response will be 0 for the 0 3 tesla range 1 for 0 6T 2 for 1 2T and 3 for the 3 0T range In order to change the range send R followed by a single numeral as defined above e g R2 will select the 1 2T range and IR will return 2 to confirm the range selection Always wait a second or two after a range change before zeroing To select the ac mode send GA To return to dc mode send GD To check which mode the teslameter is in send IG This will return D for dc A for ac plus either
30. than one teslameter or other compatible Group3 device the serial data path can be configured in an arrangement called the Group3 Communication Loop G3CL This allows convenient communication to up to 31 devices from a single computer or terminal without the need for a multiplexer The is a communication protocol defining hardware electrical and fiber optic signal parameters and a command structure based on the ASCII code All the commands applicable to the teslameter are defined in Table 9 below In the G3CL a message from external equipment computer terminal modem etc is sent to the first device in the loop This device retransmits the message to the second and so on around the loop until finally the last device sends the message back to the external unit Thus the system verifies that all devices are active and have listened to the message See Fig 9 Each device is assigned a unique address in the range 0 to 30 as set on the internal switches see section 3 6 When connected in a loop containing more than one device the devices must be set by means of an internal switch not to initiate communications themselves They may only respond to commands from the host unit In the teslameter switch S2 1 must be OFF All Group3 devices with serial communication are fitted with fiber optic transmitters and receivers as a standard feature Fiber optic cabling is particularly valuable when the loop runs in the vicinity of electricall
31. 31002 o Bof 2 551516 5 TSY v 109735 90Q0HO1UM A3lUQNOO3S Td Qx3 o 9 ri 6E T WIX 19153 5 21 L3SIY 158 26 SE F r 3 Ty MY 29 ov 5 969XuM 2 5 Ty 6 TE on oel 14 vu ee 5 gt 20 62 V bY ere v ra 27 S 1950 Sd sg 59 ov 211 0198 5950 29 52 ET ZT pz 9 y 7 aq in 2 oio z9 99 L ST 04d 14d 19 990 ov cfi 154 ety 9 Tsar pty 55 jer Ft JK e j o z 022 S N A YIHLO OL 5 Wl 0 a In N N 729 stAT ZEZXUM BE 29 7 DTM 151 serial User s Manual PROC RD CMP r C3 C gt C2 DTM 151 serial User s Manual a N Processor Board Component Overlay 16000089 JO4STS I1 AW lt v 0 88 T L6000099 30 S FS 1 JW 52445 v 0 HOT Z ST bT 59000059 103STS
32. C or V for continuous or triggered mode Select and zero each range in turn The following character strings may be used Zero all ranges RO ZR1 ZR2 ZR3 Z where indicates a 1 to 2 second pause Select and zero all ac ranges then return to dc mode GARO ZR1 ZR2 ZR3 ZGD If a single range probe is in use attempts to select another range will return the message FIXED RANGE PROBE The command F will return the field value as measured by the selected range Detailed descriptions of the digital filtering and triggering functions are given in Sections 4 6 and 4 7 DTM 151 serial User s Manual 4 13 4 6 DIGITAL FILTERING The digital teslameter software includes a digital filtering algorithm which may be invoked by an internal switch or by remote command See pages 3 8 and 4 9 Filtering is useful for smoothing out small fluctuations in the field reading In order to speed up the response to large field changes when filtering is on a window can be set to define a band about the current displayed field value Filtering will only occur while the unfiltered field value remains within the window If the field value changes rapidly enough the filtered field reading will not be able to follow fast enough to keep the unfiltered value within the window and filtering is temporarily disabled This allows the field reading to follow large rapid field changes while providing good filtering of constant or slowly varying fields The window width
33. GMW GROUP3 DTM 151 DIGITAL TESLAMETER with serial communications USER S MANUAL For units supplied with software DTMS V6 0 Distributed by GMW Associates 955 Industrial Road San Carlos CA 94070 Tel 650 802 8292 Fax 650 802 8298 Email sales gmw com website http www gmw com Manufactured by Group3 Technology Ltd PO Box 71111 Rosebank Auckland New Zealand Tel 649 828 3358 Fax 649 828 3357 Email info cgroup3technology com website www group3technology com 82010140 GM 955 Industrial Road San Carlos CA 94070 Tel 650 802 8292 Fax 650 802 8298 Email sales gmw com Web site http www gmw com Thankyou for purchasing and using a Group3 digital teslameter We hope you will join the many hundreds of users worldwide who are enthusiastic about our products Group3 has been designing and building magnetic field measuring equipment since 1983 We are constantly upgrading our products and support documentation We welcome input from our customers so if there are aspects of the instrument which you particularly like or which you would like to see improved please contact your Group3 supplier see back page for a complete list or Group3 directly with your suggestions to info group3technology com The Group3 website www group3technology com contains details of all our products This site is regularly updated so check it from time to time to learn about recent developments CONTENTS 1 General D
34. OOFT S0000189 80000089 90000089 10000059 90000579 LTOOOOLT 6660004T uo Aaab uu 6 0062 4 0 TOGL dSAaH 5 8 o u aequeuou 5sN S d W Jl04STS I1 AW 339 t O ZS XOT qod paeoq 4 DAT d1O030euuoo 3exoos edtm em gz esodand SgvIVNI peeq ANOT seyoqtms ex aooeds 1 V t R MAN 1 CU RACE Od o Dos ed cd SE e e OR 430 55 GUvOd AV IdSIG VvOOO00ST LNNWANOSVHINW OIJDZNDOVN LSIT SLNVd GHLINIT ASOIONHOXNL 41045 9111 SIN BIJ AO 1ueuoduio2 108692014 DTM 151 serial User s Manual SAVT 48000206 5 BAVOS 313348 9NIMVUO 031v0 NAM 16 0N Z 031v0 eqoag 4 019 PM M 88 29 35V9 t
35. Puts teslameter in local lockout mode The keys become inactive Pressing the keys gives display message noLOCAL Restores local operation Put in a simulated temperature to replace the real reading X cancels Turns OFF units symbol sent after field and temperature readings Turns ON units symbol sent after field and temperature readings Default set by S2 6 Put in a simulated raw field at the ADC output X cancels Put in a simulated raw field after EEPROM calibration X cancels Put in a simulated raw field after zeroing X cancels Set zero enters a zero offset n for the selected range Temperature requests a temperature reading from the teslameter Units field values displayed and sent in gauss Units field values displayed and sent in tesla Default set by S2 5 Triggers field measurement after triggered operation selected by GV Raw field returns uncalibrated field reading direct from ADC Returns raw field reading after teslameter internal calibration Like WE but field reading has user entered zero offset applied Cancels simulated field and temperature Window enters n window within which digital filtering occurs Default 1 gauss Maximum n 65534 Zeroing calls up zeroing mode and defines current field reading as zero for selected range only The ranges are individually zeroed Default sets zeroing offset to zero returns single hex character 0 through F indicating the position of the baud rate selectio
36. V commands If the field values obtained on triggering are required to reflect only the field at the time of triggering and not contain any history then filtering should be turned OFF DTM 151 serial User s Manual 4 15 4 7 3 Triggered operation timing The teslameter stores a new field value from 0 to 10ms after the V is received After storing computations are done taking about 100ms The new field value is ready for transmission no later than 120ms after the V Do not request transmission of the value using F sooner than 120 ms after the V command or the old field value may be transmitted If the teslameter is set for automatic transmission of the new value section 4 7 1 transmission will start about 120ms after the V depending on the field value Just the one triggered reading is sent on each V command 4 7 4 When the V command is ignored The V command is ignored by teslameters which have not been initialized for triggering by the GV command The V command is ignored by teslameters which have been initialized for triggering if the command is received while the device is still in the process of making a measurement in response to a previous V command 4 7 5 Zeroing while in triggered mode If the teslameter is zeroed either with the keys or by remote command while in the triggered mode a new zero offset will be calculated and stored using the last field measurement made The effect of the zero operation will be reflec
37. ace in contact with the ceramic is flat and covers the whole of the ceramic surface Do not apply more force than is required to hold the probe in place Any strain on the ceramic will alter the probe s calibration and excessive force will destroy the Hall element inside When the probe head is mounted the cable should be clamped firmly nearby so it cannot be torn away from the probe head if accidentally pulled The flexible section adjacent to the probe head can be carefully folded to allow the cable to come away in any direction but avoid repeated flexing of this section Keep the cable out of the way of foot traffic Do not pinch the cable or drop sharp or heavy objects on it A severed cable cannot be re joined without altering the probe s performance and requires factory repair and re calibration Your DTM must be used with a Group3 Hall probe The probe may be one supplied with your teslameter or it may have been obtained separately In any case calibration is preserved when probes are exchanged between instruments In order to obtain DTM 151 serial User s Manual 3 1 specified performance the DTM 151 should be used only with a 141 and 231 series probes The standard probe cable length is 2 meters Probes with non standard cable lengths up to 30 meters may be ordered from your Group3 supplier The cable used for Group3 probes is shielded to reduce pickup of induced noise from external sources Such noise may reduce the accura
38. are addressed to it B lt text gt lt cr gt Displays ASCII text on teslameter display 7 characters maximum lt gt Cancel text mode return to normal display Cn Calibrate calls up the calibrate function and defines the current field measurement as equal to the entered value n Command applies to the range selected only Separate calibration factors are stored for each range Default field measurement not modified calibration factor 1 DO Turns OFF digital filtering D1 Turns ON digital filtering Default set by S2 7 EC Erase calibration sets calibration factor to 1 on current range EL Erase scale factor sets scale factor to 1 all ranges EO Erase offset sets offset to 0 all ranges EP Erase reset peak hold field value EZ Erase zero cancels zero correction on current range F Field reading requests a field reading from the teslameter GA General function AC puts teslameter in ac field measurement mode GD General function DC puts teslameter in dc field measurement mode GC General function Continuous teslameter measures continuously GV General function Triggered teslameter measures when triggered by V DTM 151 serial User s Manual 4 9 ID IG lJ IK IL IN lO IR IZ Jn Kn Ln NH NT On RO R1 R2 R3 4 10 Inspect calibration factor returns calibration factor as mantissa and exponent Inspect digital filtering status returns 0 for OFF 1 for ON Inspect gene
39. cy of the instrument cause malfunctioning or in extreme circumstances even result in damage to the internal circuitry See section 3 12 of this manual With the DTM unpowered plug the probe connector into the instrument The pin side of the plug is inserted into the large opening in the rear of the DTM with the plug s label uppermost when the instrument is standing right way up It is easy to find the correct mating position for the plug and then push it fully home but if any difficulty is experienced at first remove the DTM s top cover by loosening the central screw and lifting the cover off Now it is possible to see when the plug is centrally located and its overhang slides over the card edge receptacle ensuring that its pins engage correctly Tighten the connector retaining screws finger tight Do not leave these screws loose as they form part of the shielding system around the teslameter The teslameter should always be used with both covers attached Always disconnect power from the teslameter before connecting or disconnecting the probe If the probe connector is inserted or withdrawn with power on data stored in memory may be corrupted leading to erroneous field readings If this happens the defaults switch S2 8 should be switched ON then OFF while power is applied See Fig 5 and page 3 9 When no probe is connected to the DTM the display reads noProbE 3 3 CONNECTING THE POWER SOURCE All teslameter versions except for the L
40. ect as apertures have to be left in the case for the display and various connectors etc The unit is a precision measuring device and should be treated with care not subjected to adverse environmental conditions The plugpacks supplied with each teslameter should be plugged in to a clean mains power supply Noise on the mains will work its way through the transformers and disturb the teslameter Simple mains filters are readily available if there is only one mains supply for the whole machine Route the low voltage lead away from high current or high voltage wiring Ideally cut the low voltage lead to the minimum length required for the installation and re connect the plug to it 3 16 DTM 151 serial User s Manual If you are using the serial communication features of the teslameter take advantage of the noise immunity of the fiber optic facilities available rather than using the wired RS 232C connection Fiber optics were included in the DTM 151 for the express purpose of providing noise free communication in hostile applications The fiber optic cables used with the DTM 151 are economical and convenient to use simpler in fact than wiring To interface the fiber optic cables to your computer or other data acquisition system use a Group3 model FTR fiber optic adaptor See section 3 8 on pages 3 12 and 3 13 fora description of the second watchdog operation Grounding the teslameter case The probe shield is terminated to the probe conn
41. ected in sequence by pressing the RANGE key Four range indicators show the range in use If a high sensitivity probe is connected to the teslameter the actual full scale ranges are one tenth of those shown above i e 0 03 0 06 0 12 and 0 3 tesla The magnetic field measurement is displayed with up to seven digits A minus sign is added to indicate reverse polarity fields Press the keys together to zero the display The display shows ZEro Field reading is filtered if selected by the internal switch see p 3 9 b AC field measurement ranges and zeroing as above Shows the value of time varying component of field This mode is indicated by A appearing in the left hand display character c Peakhold display ranges as above Displays maximum field measurement taken either polarity since entering the mode or since last reset HOLD indicator shows peak hold mode is operating If filtering is on the filtered field value is held Reset is performed by pressing both keys together The peak value is also reset if the field polarity changes 4 4 DTM 151 serial User s Manual d Peak ac measurement Combination of b and c above e Probe temperature display in celsius degrees 4 4 3 Display Messages Power up message The message GrouP 3 appears in the display for 2 seconds when the teslameter is first powered or when a serial command restarts the operating software see section 4 5 No Probe The message noProbE is displayed if
42. ector case which is then connected by the retaining screws to the teslameter chassis At this point the entire shield system is floating In some installations it is beneficial to have the system floating but most frequently it is sensible to have the shields grounded If the teslameter is panel mounted then the case is almost certainly electrically connected to the control rack and grounded that way However if the teslameter is a bench unit then the rubber and plastic feet on it will isolate the case If the case does need to be grounded then loosen one of the screws on the back panel and put a grounding lug under the head of the screw It is most convenient to use a 1 4inch 6 35mm quick connect tab The grounding wire can then be easily disconnected if the teslameter has to be moved Use a heavy gauge short wire to ground the unit to a substantial grounding point nearby If the teslameter is sitting on metalwork then it should really be grounded to that metalwork so it is at the same potential Further Preventative Measures If problems are still encountered despite following the precautions detailed above then there are some further things to try Tests have shown that in an electrically noisy environment the main path of noise entry to the teslameter is through the low voltage power supply input The trouble could come from mains borne transients working their way through the plugpack transformer or from interference picked up on
43. ed except for option L DTM 151 supports LPT 141 LPT 231 MPT 141 MPT 231 probes Options Bench style instrument with display add suffix D Panel mount version add suffix P of these options Without display plugpack powered add suffix N must be specified Without display line voltage power add suffix L Serial data input output RS 232C amp fiber optic add suffix S must select IEEE 488 GPIB capability add suffix G one option Example DTM 151 DS Probes Four ranges standard 2 meter shielded cable LPT 141 2s standard sensitivity LPT 231 2s high sensitivity MPT 141 2s probes MPT 231 2s probes Single range probes add range suffix 03 06 12 30 Special probe cable lengths change length suffix to Xs where X is the desired cable length in meters 30 max Example LPT 141 10s for 10 meter cable Accessories fiber optic cable fitted with connectors 60 meter length maximum probe holders fiber optic repeater bidirectional model FOR 2PP fiber optic to RS 232C adaptor model FTR digital display for remote control amp readout of field values model DPM rack panels 3 5 inches high 2U for rack mounting 1 2 or 3 DTMs or DPMs ferrite kit 11000036 for spark protection power supply PS12D7 for spark protection DTM 151 serial User s Manual 2 5 DTM 151 serial User s Manual 3 SETTING UP 3 1 INTRODUCTION This manual provides operating instructions for all members of t
44. en 21 OND 901 24 t 193135 92 24 2 193135 9 2 24 193135 JONVYSZ Zd 1104100 48 38426 24 YANI 4 3 16 24 Y ANI 4 34406 24 undino 339 62 29 0N9 394343438 3411933431 95 29 3SN3S 34041943431 56 24 4 3sN3S 8 1 403196 24 TWH 85 59 A TH 4 28 uno 1081N020 Zd 10N1N026 Zd AS 4338 3418 0339 1714 1 3 4 2 03123135 90d 3SNIS 3801 34031 SAd 35435 JYNLVYIdWIL 184 1 24 5 23 A 2 63 Ll d A TWH 8 24 20 uno 1031N02 61 29 tad uno 1041N02 02729 38084 TVH 01 12 24 00 22 24 700 2 29 101 5984 ATGN3SSV 335 4 231 AI SANI T1VISNI 000120 00 0 MOL OLM 64 282 180 Z 1269 Ziv ZH 13 LINO 8 4 38084 JONVY 319NIS 404 SNOILVISVA 310N 9588 OW 1 63 0v 8 24 80V 6 24 Tov 01 24 90V 4 Sov 2 24 707 1 28 Quvo8 90 OL 31 24 d Zd ZOV 61 24 iov 9 24 00 21 001 DTM 151 serial User s Manual 0000 19 46000089 00000159 04600169 81000559 00000599 81000259 90000071 40000789 60000089 12000089 90000579 10000179 AW SZHAS 339 p O SG GZ ST AW GZSUW 3394 9 0 ST 5 j u 2 9 8170
45. ence produced by high voltage discharge This description includes features of the IEEE 488 interface option which is an alternative to the serial communication option If your teslameter is the IEEE 488 version refer to the DTM 151 G User s Manual FEATURES Measures magnetic fields over four ranges up to 3 tesla with polarity indication resolution up to 1 part in 600 000 Used with special miniature Hall probe easy to attach to magnet pole or other hardware Probe holders are available as optional accessories Accuracy and temperature specifications include total system performance probe and instrument This is the only meaningful indication of measurement accuracy Probe is calibrated with field and temperature characteristics stored in memory chip contained in cable plug Basic accuracy 0 01 of reading 0 006 of full scale Microprocessor reads probe calibration data stored in probe connector and computes corrected field reading Temperature coefficient 10ppm C overall achieved using temperature sensor probe Microprocessor calculates corrected field reading Accuracy is verified against nuclear magnetic resonance NMR standard Probe calibration is verified at many field points and a printed calibration table is supplied with every probe AC mode measures and displays time varying fields between 8 Hz and 3000 Hz Front panel keys set the display to read the desired field range to read the peak value of t
46. er core has not retracted Loose cable ends should be protected from dirt and scratching 3 5 ELECTRICAL SERIAL DATA INPUT OUTPUT CONNECTIONS Serial data connections to the teslameter can be made electrically in two ways as alternatives to the fiber optic method described in the previous section 3 5 1 The G3CL Ports The two 4 way Group3 Communication Loop connectors one each for send and receive provide an electrical alternative to the fiber optic ports and handle the same data Signal levels are equivalent to RS 232C levels RS 232C handshake signals are not present at these ports The G8CL ports allow serial connections to be made using a simple twisted pair or 3 4 DTM 151 serial User s Manual coaxial cable for each data direction and avoid consideration of handshake signals if these are not required in the application Connection to the G3CL ports requires two Molex receptacles type M5051 4 with M2759 crimp terminals Pin assignments are given in Table 1 below The RS 232C standard allows cable lengths of up to 50 ft but in practice longer cables will work reliably particularly at the lower bit rates Connection is made through the labelled opening in the teslameter s rear panel In the device at the send port pin 2 common is connected to circuit common However at the receive port the signal drives an optical coupler without any direct connection to the circuitry This arrangement avoids ground loops which can inject noi
47. error in transverse plane X1 seating error on ceramic 0 4 max Fig 8 Probe Dimensions 4 3 READING THE FIELD VALUE The field value is read directly off the display A negative sign indicates that the field direction is opposite to that described in section 4 2 For maximum resolution select the lowest range which will display the field value See sections 4 1 and 4 4 for range selection instructions If the field reading is greater than full scale the message DTM 151 serial User s Manual 4 3 o rAnGE will be displayed Change to a higher range until the message clears The field may be displayed in tesla or gauss with the appropriate indicator showing the units in use To change the units see section 3 6 page 3 8 4 4 DISPLAY MODES USING THE FRONT PANEL KEYS 4 4 1 The Keys Two front panel keys are used to control the teslameter Changes of state occur as a key is released not as it is depressed The MODE key used on its own rolls the instrument through the various operating modes in sequence dc field ac field peak hold field peak hold ac field and probe temperature as described in 4 4 2 below The RANGE key selects the range without changing the display mode The keys are pressed together at the same time to zero the display The same action is used to reset the display in the peak hold mode 4 4 2 Operating Modes a Field dc display Four ranges 0 3 0 6 1 2 and 3 0 tesla full scale are sel
48. escription 1 1 2 Specifications of DTM 151 System 2 1 3 Setting Up 3 1 Introduction 3 1 3 2 Connecting the Hall Probe 3 1 3 8 Connecting the Power Source 3 2 3 4 Fiber Optic Connections 3 4 3 5 Electrical Serial Data Input Output Connections 3 4 3 6 Internal DIP Switch Settings 3 8 37 Bit Rate Selection 3 11 3 8 Second Watchdog Operation 3 12 3 9 Analog Outputs 3 13 3 10 Grounding 3 14 3 11 Installing the Panel Mount Option 3 15 3 12 Installation Techniques for Electrically Noisy Environments 3 16 4 Operating Instructions 41 Zeroing 4 1 4 2 Installing the Probe 4 2 4 3 Reading the Field Value 4 3 4 4 Display Modes Using the Front Panel Keys 4 4 4 5 Using the Serial Data Inputs amp Outputs 4 7 4 6 Digital Filtering 4 14 4 7 Triggered Operation 4 15 5 Technical Diagrams General Information 5 1 Display Board Schematic 5 2 Display Board Component Overlay 5 3 Display Board Parts List 5 3 Probe Plug Board Schematic 5 4 Probe Plug Board Component Overlay 5 5 Probe Plug Board Parts List 5 5 Processor Board Schematic 5 6 Processor Board Component Overlay 5 7 Processor Board Parts List 5 8 Analog Board Schematic 5 9 10 Analog Board Component Overlay 5 11 Analog Board Parts List 5 12 13 DTM 151 serial User s Manual Contents 1 LIST OF FIGURES Fig 1 Power Input Connections of the L option 3 3 Fig 2 RS 232 C Connector amp Jumper Locations 3 6 Fig 3 Send and Receive Jumpers 3 8 Fig 4 Option Jumpers 3 8 Fig 5 Location of P
49. for correct operation These options are provided for see below DTM 151 serial User s Manual 3 5 REAR OF UNIT RS 232 C CONNECTOR OPTION PINS 26 H 13 TXD 2 RXD m Serial Out 1 4 REC m 6 Serial Out HANDSHAKE PINS DTR 1 2 5V 8 CDI CD1 3 4 DCD 20 m 7 Signal Gnd DR1 5 m 6 5V 6 DRI 51 7 H al CTS 5 51 51 9 10 RTS 4 RSI N C 11 m12 Gnd gm m3 RX T M PINS m 2 TXI RS 232 In 1 2 14 1 Case Gnd TX1 a 1 RS 232 Out EDGE PROCESSOR BOARD Fig 2 RS 232C Connector and Jumper Locations The DTM can provide one output handshake signal RTS which is asserted high when the unit has data it wishes to transmit The DTM can also accept up to two input handshake signals CTS and DCD If CTS is held low by the external equipment then no data will be transmitted When low DCD inhibits and initializes the receive input of the teslameter DCD must be high to allow the unit to accept incoming data If these inputs are not connected to the RS 232C pin field the relevant pins must be tied to 5 volts on the Processor Board using the jumpers provided The handshake signals can be used only when the teslameter is connected directly through its RS 232C connector to an RS 232C compatible device When several Group3 devices are arranged in a loop using the Group3 Communication Loop ports RS 232C handshaking cannot be used CTS and DCD must be tied high
50. g ac component The overall response to varying fields is 8Hz to 3kHz and the rectified output has a time constant of 0 2 seconds The rectifier circuit responds to the average value of the ac waveform but is calibrated such that if the waveform is sinusoidal the reading corresponds to its rms value The output impedance is the same as for the dc output 3 10 GROUNDING All parts of the teslameter s metal case are connected together to form an integral electric shield around the circuitry inside When the probe connector is plugged into the teslameter and the retaining screws are tightened the probe connector case and the teslameter case are connected together and form an integral shield around the circuitry inside The cable shield is added to the case shield and extends protection from electrical interference almost up to the probe head Because there is an internal connection between teslameter circuit common and the probe connector case when the probe connector is engaged and the retaining screws tightened the teslameter circuit common will be connected to the case Do not make an additional connection between circuit common and the case at any point including at the RS 232C connector or at the G3CL connectors on serial teslameters or at the GPIB connector on teslameters with the IEEE 488 option Such additional connection will form a ground loop and may introduce errors in the measured field value The shielding provided with the above ar
51. ge the rate of data transmission or to request transmission of a single field reading Other commands set scaling and offset select the field range select ac and peak hold functions turn on and off digital filtering and modify the filter characteristics System status may be determined remotely The system can be operated in triggered mode where field measurements by one or more teslameters are triggered in synchronism with each other by external command Internal switches select serial data format and baud rate device address string terminators filtering field units in gauss or tesla data format service request action EOI action and perform system reset Two analog outputs are available instantaneous field value 0 to 3 kHz rectified time varying ac component of field 8 Hz to 3 kHz All model variations are available without display and keys for true black box magnetic field to computer interfacing A panel mount model with display is available 1 2 DTM 151 serial User s Manual 2 SPECIFICATIONS DTM 151 SYSTEM Measurements Field ranges Resolution Resolution Accuracy Temperature Stability Time stability Specifications include LPT 141 or MPT 141 Hall Probe field value and time varying ac component of field 0 3 0 6 1 2 3 0 tesla full scale 3 6 12 30 kilogauss full scale with polarity indication maximum calibration field 2 2 tesla 22 kilogauss DC mode with digital filtering ON
52. he DTM 151 family of digital teslameters with serial communications and their companion LPT 141 LPT 231 MPT 141 and MPT 231 series Hall probes For a summary of all current members of the product family see page 2 5 These instructions are written for a teslameter with front panel display and keys DTM 151 DS PS Users of teslameters without display and keys should ignore sections of this manual referring to these features All other aspects of operation are identical Before using your teslameter for the first time please read through sections 3 2 3 3 4 1 4 2 and 4 3 of this manual This will give a quick introduction to basic operation of the instrument you have a teslameter without display DTM 151 NS LS also read sections 3 4 3 5 3 6 3 7 and 4 5 If you have the panel mount version DTM 151 PS mounting instructions are to be found in section 3 11 For help regarding operation in electrically noisy areas see section 3 12 3 2 CONNECTING THE HALL PROBE Before handling the probe please read the following Group3 Hall probes are built to be as robust as possible for a small precision device However it is most important that certain precautions be taken when handling and installing probes so that they are not damaged or destroyed and to preserve their accurate calibration Mount the probe head so there is no pressure which will tend to bend or depress its ceramic rear surface If the probe head is clamped make sure the surf
53. he display that is if the number to be displayed is outside the range 99999 9 In overflow the instrument is not over ranged but rather the computed reading is too large to be displayed However if over ranging occurs at the same time as overflow then the over range message is displayed preferentially The usual cause of overflow is a large calibration factor scale factor or offset entered through the serial port See section 4 5 DTM 151 serial User s Manual 4 5 Reset The message rESEt appears for 1 second when defaults are reloaded either by a CTRL X command or by switching 52 8 ON No Local Control The message noLOCAL appears if a key is pressed when local control is locked out by the SO1 command See Table 9 in section 4 5 Address setting display With the teslameter in dc field display mode when the MODE key is pressed twice very quickly the display shows Addr nn where is the address of the teslameter as set switches S1 1 though S1 5 Press the mode key once again to cancel this display 4 6 DTM 151 serial User s Manual 4 5 USING THE SERIAL INPUTS AND OUTPUTS 4 5 1 Serial Connections The three bi directional serial input output ports at the rear of the teslameter can be used in various ways to connect the device to external equipment for data logging and systems applications Sections 3 4 and 3 5 give information on making connection to the ports and configuring the signal flow In systems containing more
54. he field using the peak hold function to show the ac field component and to display the probe temperature DTM 151 serial User s Manual 1 1 Peak hold is implemented digitally has zero sag Digital filtering of the displayed field reading suppresses short term fluctuations The filtering characteristic is non linear small field variations within a narrow window centered on the currently displayed value are filtered large field changes are displayed immediately Filter window and time constant may be changed by remote command Filtering is controlled by an internal switch Two digital communication options either serial RS 232C and fiber optic Or IEEE 488 General Purpose Interface Bus With the serial option a single teslameter may be connected to standard RS 232C equipment or up to 31 units may be interconnected on a Group3 Communication Loop G3CL and driven from computer or terminal Fiber optic ports duplicate functions of RS 232C signals for electrical noise immunity and voltage isolation Fiber optic links may be up to 60 meters in length using Hewlett Packard HFBR 3500 series fiber optic cables Use a Group3 fiber optic repeater to extend communication distance The IEEE 488 option fully supports all relevant GPIB functions and commands including full talker listener capability serial and parallel polling service request and talker only ASCII control commands are accepted to modify the output data format to chan
55. ic is flat and covers the whole of the ceramic surface Do not apply more force than is required to hold the probe in place Any strain on the ceramic will alter the probe s calibration and excessive force will destroy the Hall element inside When the probe head is mounted the cable should be clamped firmly nearby so it cannot be torn away from the probe head if accidentally pulled The flexible section adjacent to the probe head can be carefully folded to allow the cable to come away in any direction but avoid repeated flexing of this section Keep the cable out of the way of foot traffic Do not pinch the cable or drop sharp or heavy objects on it A severed cable cannot be re joined without altering the probe s performance and requires factory repair and re calibration The probe can be fitted to a Group3 probe holder part no 17000050 for the LPT 141 and LPT 231 part no 17000081 for the MPT 141 and MPT 231 Probe holders which orient the probe head to the axial position are also available from Group3 suppliers The holders protect probes and provide additional cable strain relief Alternatively the probe can be clamped using the machined detail in each side of the metal cap The probe will measure the component of the field which is normal to the flat surface of the probe case The point of maximum sensitivity is marked by a target printed on the top of the probe case A positive indication will be obtained when the magnetic field 4 2
56. ing data that may have been corrupted by the disturbance It is suggested that in extreme spark conditions that switch S2 8 defaults be left ON so that defaults are restored on power up hardware reset and CTRL U command 3 9 ANALOG OUTPUTS 3 9 1 Connectors Two output signals are available at the rear of the teslameter These signals are referred to as the and ac outputs and are described below The analog outputs are not corrected for linearity or temperature errors The cable connector required is a Molex receptacle type M5051 4 fitted with M2759 terminals It carries both outputs Pin assignments are given below pin signal 1 ground 2 ac output 3 ground 4 dc output Table 8 Analog Output Connector Pin Assignments 3 9 2 DC Output The dc output is the Hall probe signal amplified to 3 volts full scale and gives an indication of the instantaneous field value from dc to 3kHz 3dB with a roll off of 60dB decade Field direction is indicated by the output voltage polarity There is a small zero offset arising from the probe zero field output and amplifier offsets The output impedance is 1000 ohm with a 10nF capacitor to common for noise filtering DTM 151 serial User s Manual 3 13 3 9 3 AC Output The ac output is a positive voltage analog of the time varying or ac field component To generate this output the instrument removes the dc component of the analog output described above then full wave rectifies any remainin
57. matic 5 4 Probe Plug Board Component Overlay 5 5 Probe Plug Board Parts List 5 5 Processor Board Schematic 5 6 Processor Board Component Overlay 5 7 Processor Board Parts List 5 8 Analog Board Schematic 5 9 10 Analog Board Component Overlay 5 11 Analog Board Parts List 5 12 13 DTM 151 serial User s Manual 5 1 bare 00000S1 HOS WudSIO 9NAYSO V pubog Aojdsig P31 9 49 5 lil M ooma 2 a o 21 a e o 5 s n 9 9 lt 1 5 lt IM un 90 83113 vis3l ssnvo OO Z dWIH 9in en 10 L dSQH 8n zn Cuwoom lt a ONNINEN S1N3A23S 35 9 00 HOL HOL 4 23 AS sss lt lt 259 153 35 lt M Y lt 13838 lt osi lt c KEM fe r 2 0 oc ir 62 7 82 7 4 amp 92 17 2 1 pza ezar Tzar izar 0 6 1 91 17 51 10 vitr 6 17 8 17 9 17 sar rar E Tar DTM 151 serial User s Manual 5 2 10000589 10000809 10000409 S0000619 0000689 26000059 WvOOO
58. n switch once the command has been given changing the switch position does not alter the baud rate until some other command is sent returns a 16 bit binary number representing the states of the 16 DIP switches 0 OFF 1 ON once the command has been given changing the switches does not alter the teslameter operating mode until some other command is sent restarts operating software as if teslameter had been freshly powered up Reload defaults all default values reinstated Message RESET is sent DTM 151 serial User s Manual 4 11 4 5 3 Serial Output Messages The following error messages are transmitted under the circumstances described INVALID COMMAND ENTRY the command entered did not comply with Table 9 NUMBER TOO BIG the number entered in a command was too big POSITIVE NUMBER REQUIRED erroneous entry of minus sign DIVIDE BY ZERO a command entered a number which gave this arithmetic error RESET defaults were reloaded by CTRL X command or switching S2 8 ON NO TEMPERATURE PROBE a temperature reading was requested from a non temperature corrected probe BAD TEMPERATURE READING a temperature reading was requested from a temperature corrected probe but the temperature sensor or associated circuitry is giving an invalid reading FRAMING ERROR the wrong number of bits was sent in one or more characters of the last command OVERRUN ERROR characters were sent too quickly for the teslameter to process The
59. native power supply to be used instead of the usual plugpack The alternative power supply is model PS12D7 It is a universal voltage 85 270V 50 60Hz input 12Vdc 7W output unit with excellent input output isolation for noise and transients The PS12D7 is DIN rail mounted In conjunction with the PS12D7 we recommend the use of our ferrite kit part no 11000036 which implements the ferrite filtering measures described above The kit consists of a 1 2 meter length of twin cord with a ferrite tube fitted This cord is intended to connect between the PS12D7 and the teslameter The kit also contains a split ferrite tube and housing for fitting to the probe cable 3 18 DTM 151 serial User s Manual 4 OPERATING INSTRUCTIONS 4 1 ZEROING The DTM 151 digital teslameter has a very stable zero field reading Nevertheless it is good practice to zero the instrument on all ranges immediately prior to making critical field measurements The zeroing process takes out residual zero errors in the Hall probe and the instrument s preamplifier front end The instrument must be zeroed if it has not been powered for 30 days or more as there is a possibility that its memory back up may have failed Zeroing is mandatory if a different probe is to be used since the instrument was last zeroed You should also zero the instrument when using it for the first time The ac ranges must also be zeroed individually Before zeroing the system connect up and apply power
60. nd then switch to the desired position 3 7 BIT RATE SELECTION A 16 position switch is provided on the Processor Board for setting the serial data bit rate baud See Table 6 for switch position versus bit rate and Fig 5 for the location of the switch The baud rate must be set to match that of the communicating device switch baud position bits sec 50 110 134 5 150 200 300 600 900 1050 1200 1800 2000 2400 4800 9600 19200 7 Bit Rate Switch Settings DTM 151 serial User s Manual 3 11 3 8 SECOND WATCHDOG OPERATION The teslameter s microprocessor circuitry includes two watchdog timers The first watchdog continually monitors the operation of the microprocessor If for any reason such as a severe burst of transients occurring near the instrument the microprocessor stops running or enters an invalid mode of operation the watchdog will automatically reset the microprocessor and restart the operating program At most the user may observe a 1 to 2 second pause In very rare circumstances again caused by a particularly severe transient the processor could enter a mode of operation that fools the watchdog into believing that all was well whereas in fact the microprocessor could be running an endless loop doing nothing useful To cope with these circumstances a second watchdog is included in the circuitry The second watchdog can be set to operate in one of two modes
61. ntal conditions exceeding specifications or any other circumstance not generally acceptable for equipment of a similar type The Company reserves the right to make changes in design without incurring any obligation to modify previously manufactured units No other warranties are expressed or implied including but not limited to the implied warranties of merchantability and fitness for a particular purpose The Company is not liable for consequential damages 83000001
62. or it can be disabled as determined by the setting of a jumper on the processor board See Fig 6 1 6 seconds or the teslameter will undergo a RESTART kicked by switch scanning default the teslameter at least every kicked by serial data receive CH disabled send serial character to Second Watchdog select jumper Second Watchdog select Fig 6 Location of Second Watchdog Select Jumper 3 12 DTM 151 serial User s Manual Mode 1 default senses 1 second pulse from the switch scanning circuit This mode adds to the effectiveness of the first watchdog and like the first watchdog its operation is automatic and needs no operator intervention Mode 2 senses the received serial data If this mode is selected the teslameter cannot be used stand alone bench instrument It is necessary for the teslameter to be in continuous communication with an external control computer The computer can force a hardware reset by withholding communications for more than 1 6 seconds To maintain continuous normal teslameter operation the computer must send at least 1 character every 1 6 seconds or less If the computer determines that the teslameter is not responding to commands or is sending erroneous data it can reset the teslameter as described above Once normal operation has been restored it is sometimes useful for the computer to issue the CTRL X command to reload default numerical values and switch settings thus correct
63. plemented digitally with zero sag or decay Displays time varying ac component of field frequency response 8 Hz to 3 kHz at 3dB points response time constant 0 2 seconds average responding reads rms value of sinusoidally varying field reading is not linearity or temperature corrected 7 character 7 segment alphanumeric display 8 back lit legends for 0 3 0 6 1 2 3 0 tesla range selected peak hold mode on digital filtering on tesla gauss field units magnetic field peak hold field ac field peak ac field field value filtering smooths out small fluctuations in the reading large rapid field changes are not filtered internally switch selected 2 keys for range selection access to display modes zeroing field display peak hold reset serial option RS 232C and fiber optic parallel option IEEE 488 General Purpose Interface Bus ASCII input commands and output responses requests for field values setting and inspection of display and control modes field measurement triggering entry of numerical values setting units output data format and filter characteristics test commands field value in tesla or gauss followed by optional T or G and string terminator s system status numerical data requested by commands messages DTM 151 serial User s Manual Serial bit rate System orientation Fiber optic cable On board switches Analog outputs 488 functions GPIB connector 16
64. r the command V This is the only command which is simultaneously obeyed by more than one device on the loop the V is not to be preceded by an address command all devices which have been set for triggered operation by the GV command will respond to the V The new measurement will immediately appear on the teslameter display and can be read on the serial output by entering the F command The following sections describe details of triggered operation 4 7 1 Automatic transmission of new measurement When a teslameter is used on its own as the only device in G3CL the field measurement triggered by V will then be transmitted immediately if the device has been set for continuous transmission by the SM1 command or if S2 1 is ON with the address set to zero see page 3 9 If the teslameter has been initialized by the SMO command or if S2 1 is OFF or if the device address is not zero the new measurement will not be transmitted until the F command is entered In multi device systems each teslameter should be set NOT to send the new reading automatically each device must be read out individually by addressing it An then requesting a field value using F 4 7 2 Digital filtering with triggered operation If filtering is ON then each time a measurement is triggered the filtering algorithm will calculate a new field value for display and transmission as described in section 4 6 The effective time constant will depend on the timing of the
65. ral function returns two letters D for dc field mode or A for ac mode followed by C for continuous or V for triggered measurements Inspect filter factor returns filter factor as mantissa and exponent Inspect sampling interval returns interval in seconds between output field readings 0 implies readings sent at maximum rate Inspect scale factor returns current scale factor Inspect display mode returns H for hold display N for normal field display T for temperature display Inspect offset returns current value of offset Inspect range returns 0 for 0 3 tesla range 1 for 0 6 tesla range 2 for 1 2 tesla range 3 for 3 0 tesla range Inspect window returns current value of window within which digital filtering operates Inspect zero returns current zeroing offset added to field values Filter factor enters filter factor n Default n 41 n or 1 no filtering n gt 1 filtering more severe as n increases max 65534 0 n lt 1 reading overshoots Sampling interval enters interval between output field values Default n 0 every reading sent rate is 10 samples second n any integer time in seconds between output field values maximum n 65534 approx 18 hours Scale computes a scale factor to make the field reading equal to the entered value n The one scale factor applies to all ranges The computed scale factor may be in the range 9 9999 to 9 9999 Default field measurement not modified scale factor 1
66. rangement should be sufficient protection against EMI in most cases especially when the probe cable is shielded Sometimes it may be found helpful to ground the teslameter case to a good electrical ground point Connection can be made to the case by inserting an appropriate lug or terminal under the head of one of the rear panel fixing screws Further protection from transient interference can be obtained by using model PS12D7 power supply in place of the usual plugpack supplied with the teslameter and by installing the Groups ferrite kit part no 11000036 See section 3 12 of this manual For electrical safety the case of the L version must be grounded through the third wire of the power input cord 3 14 DTM 151 serial User s Manual 3 11 INSTALLING THE PANEL MOUNT OPTION Model DTM 151 PS is supplied fitted with a special front bezel which has threaded studs to allow panel mounting A panel mount support bracket part 17000058 is included to help support the teslameter Group3 can supply 19 inch wide 2U 3 5 high rack panels to hold one two or three teslameters parts 17000025 17000026 and 17000027 respectively Alternatively the user can mount the teslameter in any panel of thickness up to 3 16 4 76mm Dimensions for the cutout and drilled holes are shown below in Fig 7 Bezel Outline 45 52 56 ee ee a ee 127 4 holes 137 032 145 all dimensions in mm Fig 7 Panel Cutout Dimen
67. rates switch selected 50 110 134 5 150 200 300 600 900 1050 1200 1800 2000 2400 4800 9600 19200 baud Group3 Communication Loop G3CL using serial ports simple loop for 31 devices no multiplexer required GPIB with IEEE 488 option Hewlett Packard HFBR 3500 60 meters max Fiber optic repeater available for extended communications serial baud bit rate selection load defaults device address filtering string terminators data format service request enable EOI enable dc output instantaneous field analog full scale output 3V nominal source impedance 1000W accuracy 10 bandwidth 3kHz at 3dB rolloff 3 pole 60dB decade ac output rectified analog of time varying ac field frequency response 8Hz to 3kHz at 3dB points time constant 0 2 seconds average responding delivers rms value of sinusoidal field full scale output 3V nominal source impedance 1000W accuracy 12 SH1 source handshake capability AH1 acceptor handshake capability T5 talker basic talker serial poll talk only mode unaddressed to talk if addressed to listen TEO no address extension talker capability L4 listener basic listener unaddressed to listen if addressed to talk LEO no address extension listener capability SR1 service request capability RLO no remote local capability PP1 parallel poll capability configured by controller DC1 device clear capability DT1 device trigger capability CO controller capability
68. rocessor Board Switches 3 9 Fig 6 Location of Second Watchdog Select Jumper 3 12 Fig 7 Panel Cutout Dimensions 3 15 Fig 8 Probe Dimensions 4 3 Fig 9 1 Alternative Configurations 4 8 Display Board Schematic 5 2 Display Board Component Overlay 5 3 Display Board Parts List 5 3 Probe Plug Board Schematic 5 4 Probe Plug Board Component Overlay 5 5 Probe Plug Board Parts List 5 5 Processor Board Schematic 5 6 Processor Board Component Overlay 5 7 Processor Board Parts List 5 8 Analog Board Schematic 5 9 10 Analog Board Component Overlay 5 11 Analog Board Parts List 5 12 13 LIST OF TABLES Table 1 G3CL Connector Pin Assignments 3 5 Table2 RS 232 C Connector Pin Assignments Terminal Mode 3 7 Table3 RS 232 C Connector Pin Assignments Modem Mode 3 7 Table 4 DIP Switch Functions 3 9 Table5 Serial Data Format Switch Settings 3 10 Table 6 String Terminator Switch Settings 3 10 Table 7 Rate Switch Settings 3 11 Table 8 Analog Output Connector Pin Assignments 3 13 Table 9 DTM Serial Commands 4 9 Contents 2 DTM 151 serial User s Manual 1 GENERAL DESCRIPTION The DTM 151 S Digital Teslameters offer accurate high resolution measurement magnetic flux densities with direct digital readout in tesla or gauss and serial communications by fiber optics or RS 232C for system applications The instruments are light and compact and the probes are easy to use The DTM 151 has been engineered to withstand the severe electrical interfer
69. se into the link and give rise to transmission errors pin use 1 signal active 2 signal common 3 cable shield optional 4 not used Table 1 G3CL Connector Pin Assignments 3 5 2 The RS 232C Connector The RS 232C connector is a 26 pin field which can be used to connect the teslameter to a computer terminal printer or other external equipment which can send and receive RS 232C signals The pin field will connect with a standard 26 way flat cable socket connector for example 3M type 3399 6000 The pin assignments follow those of the standard 25 way RS 232C connector starting at pin 1 and omitting pin 26 If desired an adaptor cable may be used to allow cables with 25D connectors to be plugged in to the teslameter In order to avoid the conflicts and confusion which often arise when RS 232C is used to interconnect equipment which cannot be classified strictly as either communications or terminal equipment the DTM has been provided with a number of user options in the form of moveable jumpers and wire wrap posts on the Processor Board Thus pins 2 and 3 may be connected to send and receive signals respectively or vice versa Similarly a number of the most used RS 232C handshake signals are provided on the board and these may be routed to appropriate pins on the connector if desired But their use is optional In most cases no active handshaking need be used Some external equipment may require certain signal lines to be held high
70. seAT od JNZZ O T vo UuUG zZ OdN 44222 T D ded JULY T 85 2 4049 T LE D deo OTURTTOUOM JULY Z 96 86 2 AGZ ANOOT T Uuc z AUT TE 2 T o 2 zeqseAtTod 2 402270 T 2 UuG z T 62 2 4406 T 82 2 ANOT LT 2 deox zeqzseATod 2 T 9c D peeq ASE ANT T GZ uug z deo pezr e3eu T vz 40012 52 55 D ANOZZ T TZ Q peeq 4 22 T JUOT zo T 6T 2 NOT T LT 9 AGE ANT T ded
71. sions To fit the teslameter to the panel first remove the nuts and washers from the bezel studs Push the teslameter through the panel from the front making sure all the studs fit through the small holes While holding the teslameter in place place the support bracket under the teslameter from the rear pushing it up to the panel with the studs through the holes in the bracket Put the flat washers on the studs then the lockwashers and finally screw on the nuts Make sure the teslameter is resting on the bracket then tighten the nuts preferably using a long stemmed nut driver DTM 151 serial User s Manual 3 15 3 12 INSTALLATION TECHNIQUES FOR ELECTRICALLY NOISY ENVIRONMENTS The DTM 151 is a precision electronic measuring device Because of the nature of the measurements it is asked to do it is frequently exposed to conditions that are considerably worse than are normally encountered by precision instruments Therefore the teslameter has been carefully engineered to be as immune as possible to sparks and other forms of interference through the use of several kinds of power input filtering and a special high isolation switchmode power module built into its circuitry The design has been verified by extensive testing using high energy sparking in close proximity to both the teslameter instrument case and the probe Nevertheless due care should always be taken when installing the teslameter system The teslameter and its probe must be
72. ted in the next field measurement when the V command is given To ensure the most accurate zero it is best to place the teslameter in continuous mode with filtering on allow time for the display to settle then give the zero command The unit will zero correctly in triggered mode if first the V command is given while the probe is in zero field with filtering off then the Z command or pressing both keys together will zero the instrument 4 16 DTM 151 serial User s Manual 5 TECHNICAL The schematics component overlays and parts lists of the four circuit boards in the DTM 151 serial I O teslameter and probe are provided for general reference It is not recommended that the user attempt repair or servicing because in many cases replacing parts will affect the calibration of the instrument In case of trouble malfunction we strongly recommend that the user first contact the local distributor or Group3 directly for advice as to the best procedure for addressing the problem Group3 may be contacted at the address below Group3 Technology Ltd Physical address 2 Charann Place Avondale Auckland 1007 New Zealand Postal address P O Box 71 111 Rosebank Auckland 1230 New Zealand Tel 64 9 828 3358 Fax 64 9 828 3357 email info group3technology com website http www group3technology com diagram page Display Board Schematic 5 2 Display Board Component Overlay 5 3 Display Board Parts List 5 3 Probe Plug Board Sche
73. the Hall probe is disconnected from the instrument While the message is visible all key functions are disabled No Temperature Sensor The message noPrb C is displayed for 2 seconds after the Group3 power up message if the probe is not a temperature corrected type e g LPT 130 LPT 230 MPT 132 MPT 230 The message is also displayed if the MODE key is pressed to display what would have been the probe temperature reading This message warns the user that the field reading is not temperature corrected and therefore the accuracy will be less than would be obtained with a temperature corrected probe LPT MPT 141 231 Temperature Error The message is displayed in place of the temperature reading if a temperature corrected probe is in use but there is a fault with the probe s temperature sensor or associated wiring or circuitry Again this is to warn the user that the field reading will not be to full accuracy Over range The message o rAnGE appears when the DTM is displaying dc or ac field or is in peak hold if the field measurement exceeds the instrument s input capacity To clear the over range message select a higher range or reduce the magnetic field at the probe or both if necessary During over range all key operations are locked out except for range selection Overflow The message o FLo is displayed in dc or ac field modes or in peak hold mode if the computed value of the field reading exceeds the capacity of t
74. the low voltage lead itself The quickest and simplest fix for this problem is to wind the power lead several times through a ferrite core Use a thick walled ferrite tube of substantial size a simple small torroid is not nearly as effective A suggested ferrite is the TDK part number HF70RH26x29x13 This is a tubular ferrite 29 mm long 26mm outside diameter and 13mm inside diameter Winding the power lead four times through this core really close to the teslameter significantly reduces noise upsets DTM 151 serial User s Manual 3 17 If the analog outputs wired up then shielded twisted pair should be used for all wiring routed away from any high current or high voltage cabling In a really noisy environment it can be beneficial to put this analog cabling through a ferrite tube for a few turns to suppress induced noise The probe cable itself can be passed through a ferrite core The internal diameter will need to be sufficient to pass the probe head through An MPT miniature probe head is nearly the same size as shielded cable 6 5mm diameter but an LPT probe head needs an internal ferrite diameter of 14mm or more Alternatively a split core ferrite variety can be used such as TDK part HF70RU16x28x9 The core should be placed where the probe cable enters the probe connector and optionally a second ferrite can be placed where the cable shield layer ends approximately 300mm back from the probe head Group3 can supply an alter
75. ther as a single unit or in a GS3CL of various Group3 devices are set out in Table 9 below In order to gain familiarity with the commands it is recommended that you connect the teslameter to a terminal The commands can then be typed in from the keyboard and the responses observed on the terminal s screen 4 8 DTM 151 serial User s Manual The commands are in the form of one to three characters in some cases followed by a decimal number represented by n inthe table Such numeric commands must be terminated by a carriage return lt cr gt character If no number is entered where one is expected the command is ignored A decimal point is not required in whole number entries Numerical values entered by commands are retained in non volatile memory when power is off Default values shown below apply after system reset command CTRL X or if S2 8 is ON The processor automatically executes a reset if the memory back up has failed after more than 30 days without power applied Switch selectable defaults are instated on power up reset and when a switch setting is changed See Table 4 page 3 9 All responses from the teslameter start with a space character Decimal numbers include a decimal point Some are in exponential format If an error message is returned the complete command must be re entered Table 9 DTM Serial Commands command description An Address indicates to the device of address n n 0 to 30 that all following commands
76. urred The zeroing process should now be repeated for all the remaining ranges Press the RANGE key to select another range and zero this range by pressing both keys together as above After changing ranges wait 1 or 2 seconds before zeroing Continue until all the ranges have been zeroed DTM 151 serial User s Manual 4 1 zero the ranges first select the ac mode by pressing the MODE key once will appear at the left of the main display Now perform the zeroing function on all ranges as described above Because the ac measurement circuitry has a 0 2 second time constant allow the display to settle after changing ranges before zeroing Return to normal field display by pressing the MODE key 4 times Once the zeroing process has been completed the internal processor will apply the appropriate correction to whichever range is selected It is recommended that the instrument be re zeroed if the ambient temperature has changed significantly 4 2 INSTALLING THE PROBE Group3 Hall probes are built to be as robust as possible fora small precision device However it is most important that certain precautions be taken when handling and installing probes so that they are not damaged or destroyed and to preserve their accurate calibration Mount the probe head so there is no pressure which will tend to bend or depress its ceramic rear surface If the probe head is clamped make sure the surface in contact with the ceram
77. wo sets of DIP switches allowing the user to set up teslameter operation and communications according to system requirements To obtain access to the switches turn the DTM over and take off the bottom cover by loosening the single central screw Refer to Fig 5 for switch locations Switch functions are as follows 51 8 DIP switch sets device address sets serial data format number of data bits parity and number of stop bits 52 8 way DIP switch selects operation mode and communication mode 3 8 DTM 151 serial User s Manual 52 1 52 2 52 3 52 4 52 5 52 6 52 7 52 8 Fig 5 Location of Processor Board Switches Detailed DIP switch settings are given in Tables 4 and 5 below switch function switch OFF switch ON S1 1 set device address adds 0 to address adds 1 to address 51 2 set device address adds 0 to address adds 2 to address 51 3 set device address adds 0 to address adds 4 to address S1 4 set device address adds 0 to address adds 8 to address S1 5 set device address adds 0 to address adds 16 to address S1 6 maximum valid address 30 S1 7 serial data format see Table 5 for encoding format 51 8 52 1 transmission mode on demand only every reading sent 52 2 line feed carriage return S2 3 double terminator disabled enabled S2 4 echo commands echo OFF echo ON 52 5 field units tesla gauss S2 6 units symbol no symbol symbol after data 52 7 digital filtering filtering OFF
78. y noisy equipment or when voltage isolation is required The system uses the Hewlett Packard HFBR 3500 series fiber optic cables Individual cable sections between devices may be up to 60 metres in length A Group3 model FOR repeater can be used to extend communications Use a Group3 model FTR fiber optic to RS 232C adaptor to connect the fiber optic cables to a standard 25 way D type RS 232C receptacle on your computer or terminal Electrical serial data connections to the RS 232C standard are provided on Group 3 serial devices There are two possible configurations of the loop using electrical signals as shown in Fig 9 One arrangement uses the RS 232 connection between the host equipment and one of the devices on the loop The rest of the loop is connected via the ports either electrical or fiber optic or a mixture DTM 151 serial User s Manual 4 7 r Group Devices maximum of 31 Group3 Communication Loop Fiber Optic or Electrical pa Groups Devices maximum of 31 Computer Group3 Communication Loop Fiber Optic or Electrical Fig 9 G3CL Alternative Configurations The second arrangement uses the G3CL ports on every device Observe the option jumper settings required as shown on page 3 8 Fig 4 Note that the fiber optic and electrical G3CL ports are functionally identical and completely interchangeable in use 4 5 2 DTM 151 Serial Commands The commands which can be used with the teslameter ei

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