- 1 - User`s Manual: Series 250T Model 250T Frequency
Contents
1. 1 User s Manual Series 250T Model 250T Frequency Input Two Wire Transmitters Table of Contents Page Introduction 1 Description 1 Specifications 2 Specifications Display Option 4 Installation 4 Calibration 5 General Maintenance 6 List of Drawings Page Typical Installation amp Simplified Schematic 4501 077 7 Electrical Connections DC C V Input 4501 093 7 Configuration Jumper Location 4501 095 8 Dimensions DIN Rail Mounting 4501 080 9 Dimensions Surface amp Snaptrack Mtg 4501 081 9 Mechanical Assy Mtg XP Enclosures 4501 082 10 NEMA 4 amp 12 Enclosures 4501 083 10 Explosion Proof Enclosure 4501 084 11 Explosion Proof Enclosure with Window 4501 085 11 IMPORTANT SAFETY CONSIDERATIONS It is very important for the user to consider the possible adverse effects of power wiring component sensor or software failures in designing any type of control or monitoring system This is especially important where economic property loss or human life is involved It is important that the user employ satisfactory overall system design It is agreed between the Buyer and Acromag that this is the Buyer s responsibility Acromag Inc Tel 248 624 1541 30765 South Wixom Road FAX 248 624 9234 P O Box 437 Wixom Michigan 48393 7037 USA Copyright 1991 1994 Acromag Inc Printed in the USA Data and specifications are subject to change without notice 8500 286 E01K012 INTRODUCTIO2. DC 60 120 Hz ripple 0 01 of output span per volt peak to peak of power supply ripple Input Circuit Open Response Down scale drive standard Bipolar Input Configuration configured by internal jumper Threshold 0 0V DC Input Amplitude 25mV to 150V RMS Hysteresis Fixed 25mV nominal The switching points are 25mV and 25mV nominal or 0 0V 0 025V Unipolar Input Configuration configured by internal jumper Threshold 1 5V DC Attenuator resistors may be installed on the PC board to further reduce sensitivity by raising the threshold level consult factory Hysteresis Fixed 25mV nominal The switching points are 1 525V and 1 475V nominal or 1 5V 0 025V Input Amplitude 0 to 2V to 150V RMS Unipolar Excitation Supply In unipolar mode the L terminal provides an excitation supply for contact closure or open collector transistor switching circuits Nominal excitation pull up is 5V DC through 15K ohms 0 333mA nominal Note If input leads are long capacitance developed across the input leads could limit use to lower frequencies Minimum Pulse Width 10uS minimum required Reference Test Conditions Input 0 12 800 Hz 100 ohm resistive source Output 4 20mA into 500 ohm load 77oF 25oC 24V DC supply Accuracy 0 1 of calibrated span The error includes the combined effects of transmitter repeatability hysteresis terminal point linearity and adjustme
3. The linear display option assembly includes zero and span trim adjustments Display Options include xxD1 Standard Display Option D1 The minimum and maximum input any calibration is represented by 00 0 and 100 0 on the display normalized It also represents the 4 to 20mA transmitter output a resolution of 0 1 of span xxD2 Temperature Display Option D2 Not applicable xxD3 Engineering Units Display Option D3 The minimum and maximum display readings correspond to the minimum and maximum display readings specified for the unit by the customer Display Range The minimum display reading can be from 1999 to 1999 counts while the span range can be from 100 to 2000 counts span counts maximum counts minus minimum counts Note mentally remove the decimal point to determine the display counts The decimal point is configured as required such as 00 0 to 100 0 Display Characteristics The 7 segment reflective Liquid Crystal Display LCD contains 3 1 2 digits 1999 with 1 2 inch character height Also includes a factory programmed 3 position decimal point Optimal view angle is 60 degrees No Output Burden Provides a visual indication of the transmitter output without reducing the output compliance the allowable load resistance range Display Ambient Temperature Range Operating 0 to 50oC 32 to 122oF Storage 20 to 70oC 4oF to 158oF Over range The three lower order digits blank for gt 199
4. 4 amp 6 Noise Rejection Common Mode 115dB 60 Hz 100 ohm unbalance typical Radiated Field Immunity RFI Complies with IEC1000 4 3 3 V m 80 to 1000MHz AM amp 900MHz keyed and European Norm EN50082 1 with error less than 1 0 of FSR Conductive Immunity Complies with IEC1000 4 6 3 V m 15 to 80MHz and European Norm EN50082 1 with error less than 1 0 of FSR Electromagnetic Interference Immunity EMI Error is less than 0 25 of FSR under the influence of EMI from switching solenoids commutator motors and drill motors Electrostatic Discharge Immunity ESD Complies with IEC1000 4 2 Level 3 and European Norm EN50082 1 Surge Immunity Complies with IEC1000 4 5 Level 1 0 5KV and European Norm EN50082 1 Electric Fast Transient Immunity EFT Complies with IEC1000 4 4 Level 3 and European Norm EN50082 1 Radiated Emissions Complies with European Norm EN50081 1 for class B equipment Construction Basic Transmitter Circuit Boards Military grade FR 4 epoxy glass circuit board Circuit Board Coating Fungus resistant acrylic conformal coat Terminals Compression type wire size 14 AWG max Mounting Position Position insensitive Case Self extinguishing NYLON Type 6 6 polyamide thermoplastic UL94 V 2 color black General Purpose NEMA Type 1 enclosure MOUNTING DISPLAY A wide variety of mounting options and enclosures are available to meet the needs of the installation The available models
5. are listed below The transmitter is shipped as a complete assembly General Purpose Housing Available with various mounting options listed below Case Self extinguishing NYLON Type 6 6 polyamide thermoplastic UL94 V 2 color black DIN General Purpose Housing DIN Rail Mount G amp T rails G Rail 32mm Type EN50035 T Rail 35mm Type EN50022 Refer to Drawing 4501 080 for outline and clearance dimensions Shipping Weight 1 pound 0 45Kg packed SM General Purpose Housing Surface Mount Refer to Drawing 4501 081 for outline and clearance dimensions Shipping Weight 1 pound 0 45Kg packed ST General Purpose Housing SNAPTRACK Refer to Drawing 4501 081 for outline and clearance dimensions Shipping Weight 1 pound 0 45Kg packed SNAPTRACK is a registered trademark of Reed Devices Inc NEMA 4 and 12 Enclosures Option types listed below Refer to Drawing 4501 083 for outline and clearance dimensions Transmitter is mounted within enclosure at the factory These enclosures may accommodate a second transmitter with the surface mount option SM option ordered separately Conduit mounting holes and fittings are customer supplied N4 Water Tight Enclosure NEMA 4 Enclosure material and finish 0 075 and 0 060 inch thick steel with gray hammertone enamel finish inside and out Shipping weight 6 pounds 2 7Kg packed N12 Oil Tight Enclosure NEMA 12 Enclosure material and finish 0 075 and 0 060 in
6. can be mounted to either the T or G Rail Installation of the transmitter to the rail depends on the type of DIN rail used see Drawing 4501 080 Units can be mounted side by side on 1 0 inch centers if required 2 Surface Mounting Secure the transmitter to the designated mounting surface using two 6 32 screws Note that the mounting bracket has screw slots to facilitate mounting Units can be mounted side by side on 1 0 inch centers if required 3 SNAPTRACK Mounting Secure the SNAPTRACK mounting channel to the designated mounting surface using suitable fastening hardware To install the unit in the mounting channel place the bottom end of the mounting bracket between the rails and press the top notched end firmly until the bracket snaps into place To remove the transmitter insert a screwdriver into the upper arm of the connector twist to release the unit from the track and tip the unit out Units can be mounted side by side on 1 0 inch centers if required 4 NEMA 4 amp 12 Enclosure Mounting Secure the enclosure assembly to the designated mounting surface using appropriate hardware The transmitter is secured within this enclosure using two screws Note It is recommended that the transmitter be removed from the enclosure during the process of drilling holes installing fittings and mounting the enclosure 5 Explosion Proof Mounting Secure the enclosure assembly to the designated mounting position using appropriat
7. 9 counts Display Accuracy 0 1 of reading 2 counts Display Ambient Temperature Effect 0 02 per oC 0 012 per oF typical Conversion Rate 2 5 per second CERTIFICATION Consult the factory for current information on the availability of agency e g Canadian Standards Association Factory Mutual etc approvals NCR No Certification Required INSTALLATION The transmitter is packaged in a general purpose plastic housing and optionally mounted within a variety of protective enclosures The transmitter should be located in an area that is protected from dust moisture and corrosive atmospheres The enclosure type determines the protection afforded in a particular environment and location make sure that this is not compromised Maximum operating ambient temperatures should be within 13 oF to 185oF 25 oC to 85oC for satisfactory performance If unit is factory calibrated it is ready for installation Connect as shown in Connection Drawing 4501 093 If unit is not factory calibrated refer to the CALIBRATION section Mounting Mount transmitter assembly refer to appropriate outline drawing for mounting and clearance dimensions Determine which configuration is utilized and consult the proper mounting instructions listed below 1 DIN Rail Mounting Using suitable fastening hardware secure the DIN rail to the designated mounting surface A transmitter ordered with the DIN Rail mounting option DIN
8. N These instructions cover the model types listed in Table 1 below Supplementary sheets are attached for units with special options or features Table 1 A Model Number Format 250T Input Mounting Display Certification Calibration B Typical Model Number 250T FQ1 XP NCR C Series Input Mtg Display Certification Calib 250T FQ1 DIN NCR Blank SM Approval2 C1 ST N4 N12 XP XPD1 XPD2 XPD3 Notes Table 1 1 Unit can be ordered with or without the factory calibration C option All other input types automatically include calibration to customer specifications no C needed Any customer specified calibration info will be included on a separate calibration label on the unit 2 Consult the factory for current information on agency e g Canadian Standards Association etc approvals DESCRIPTION The Model 250T Frequency Input Two Wire Transmitter accepts a periodic or pulse waveform signal such as those originating from tachometers magnetic transducers and turbine flow meters and provides a 4 20mA process current output directly proportional to the signal frequency The input circuit is direct coupled fully isolated and can accept signal amplitudes from 25mV to 150V RMS Any one of ten input frequency ranges from 25 Hz to 25 600 Hz spans can be easily selected by changing one jumper shunt on a digital divider network These transmitters are RFI protected operate over a wide t
9. ch thick steel with gray hammertone enamel finish inside and out Ship weight 6 pounds 2 7Kg packed Explosion Proof Water Tight Enclosures Option types listed below Refer to Drawing 4501 084 no display window or Drawing 4501 085 with display window for outline and clearance dimensions Enclosure Materials Body and cover Copper free aluminum less than 0 4 Glass lens Heat tempered glass Gasket Neoprene Finish Corro free epoxy powder coat color gray Hub size 0 75 inch Quantity 2 Housing meets Class I Groups B C amp D Class II Groups E F amp G Class III and NEMA 4 water tight requirements Transmitter is mounted within enclosure at factory XP Explosion Proof Water Tight Enclosure No Window Shipping weight 5 pounds 2 3Kg packed XPD1 Explosion Proof Water Tight Enclosure With Window Includes the Standard Display Option D1 Shipping weight 6 pounds 2 7Kg packed XPD2 Explosion Proof Water Tight Enclosure With Window Includes the Temperature Display Option D2 Shipping weight 6 pounds 2 7Kg packed XPD3 Explosion Proof Water Tight Enclosure With Window Includes the Engineering Units Display Option D3 Shipping weight 6 pounds 2 7Kg packed Series 250T User s Manual Frequency ___________________________________________________________________________________________ 4 DISPLAY OPTION The Display is available as an option when specifying the XP Housing
10. e hardware Note It is recommended that the transmitter be removed from the enclosure during the process of mounting the enclosure To remove unit from the enclosure remove the two screws securing it to the bottom of the enclosure After enclosure is installed install the transmitter into enclosure Position the unit at an angle that permits all wiring to be routed unobstructed through both ports If the transmitter has the display option make sure the orientation of the display allows for easy reading once installed Secure the transmitter assembly to the enclosure using two screws Electrical Connections The wire size used to connect the unit to the control system is not critical All terminal strips can accommodate wire from 14 26 AWG Strip back wire insulation 1 4 inch on each lead before installing into the terminal block Input wiring may be shielded or unshielded twisted pair Output wires should be twisted pair Since common mode voltages can exist on signal wiring adequate wire insulation should be used and proper wiring practices followed It is recommended that the output power wiring be separated from the signal wiring for safety as well as for low noise pickup Series 250T User s Manual Frequency ___________________________________________________________________________________________ 5 1 Output Power Connect DC power supply and load per connection diagram refer to Drawing 4501 093 These transmitters operate f
11. ection provides information for unit configuration and calibration If the unit was factory calibrated jumpers have been placed in their proper positions and verification of the calibration can be made per the Adjustment Procedure If the calibration of the unit is to be changed first go to the Shunt Block Configuration Procedure before going to the Transmitter Adjustment Procedure 1 Transmitter Shunt Block Configuration Procedure The Frequency transmitter is quite universal in that it can be configured for Unipolar or Bipolar input signals a large number of frequency ranges and ripple response filtering Before the adjustment procedure can proceed the jumpers have to be configured to the requirements of the application refer to Drawing 4501 095 To gain access to the Configuration Jumpers remove transmitter from the installation first Second remove the circuit boards from the plastic enclosure as described in the Jumper Configuration procedure below Third configure jumpers shunt blocks as described in the Jumper Configuration procedure below Note calibration per the Adjustment Procedure should be performed before the circuit boards are reassembled within the plastic enclosure Disassembly Procedure for the 250T Plastic Housing The plastic housing has no screws and snaps together A flat head screwdriver Acromag 5021 216 or equivalent is needed to pry the housing apart as described in the following steps CAUTION D
12. emperature range and feature excellent temperature coefficients which minimize the effects from harsh plant environments Other features of this unit include the following A quartz crystal time base design is used for improved temperature performance Three filter network time constants field selectable are provided to optimize output response time and ripple characteristics Two input threshold circuits are provided field selectable Series 250T User s Manual Frequency ___________________________________________________________________________________________ 2 One for bipolar zero crossing signals and one for unipolar nonzero crossing signals In the bipolar mode the transmitter has a zero volt threshold and fixed hysteresis If configured in the unipolar mode the module has a 1 5 volt threshold and fixed hysteresis In addition the unipolar mode provides an excitation or pull up circuit This excitation allows interfacing to passive frequency inputs such as with dry rated contact closure and open collector transistor switching Following basic two wire design the output and the DC power share the same pair of twisted copper wires The transmitter acts similar to a variable resistor in series with the load and DC supply and provides an output loop current proportional to the input sensor signal See Drawing 4501 077 for a typical installation The transmitter is available for DIN rail mounting Surface Mounting 3 inc
13. h SNAPTRACK plastic rail mounting or in various housings These housings include NEMA 4 12 and explosion proof enclosures The model number specifies the mounting enclosure type The transmitter mounted in the explosion proof enclosure is available with a 3 1 2 digit LCD 1 2 inch height readout for a visual indication of the transmitter s output The readout is available as a percent of span or engineering units scaled to customer requirements Input wiring is inserted in the bottom of the unit while output wiring is inserted on the top of the unit Screws to secure the wiring are located on the front panel Connectors are screw clamp type and accept wire size up to 14 AWG SPECIFICATIONS Function This two wire transmitter accepts a frequency periodic or pulse waveform input signal provides input circuit isolation and converts this signal to a 4 20mA process current output Wide range zero and span adjustments utilize 22 turn potentiometers accessible from the front of the unit The transmitter has various mounting and enclosure options MODEL SERIES 250T INPUT Frequency direct coupled input span ranges 25 to 25 600 Hz input impedance 50 000 ohms typical Input span and zero ranges are adjustable as specified below except for special ranges which are factory calibrated per customer specifications FQ1 Frequency Span 25 to 25 600Hz Zero 0 20 of Span The input span is continuously adjustable over the pre se
14. lected input span range The minimum input frequency for any range can be from 0 20 of full scale frequency FQ Range A Span 25 to 50 Hz FQ Range B Span 50 to 100 Hz FQ Range C Span 100 to 200 Hz FQ Range D Span 200 to 400 Hz FQ Range E Span 400 to 800 Hz FQ Range F Span 800 to 1 600 Hz FQ Range G Span 1 600 to 3 200 Hz FQ Range H Span 3 200 to 6 400 Hz FQ Range I Span 6 400 to 12 800 Hz FQ Range J Span 12 800 to 25 600 Hz Isolation The input circuit is electrically isolated from output power circuits allowing the input to operate at up to 250V AC or 354V DC off ground on a continuous basis will withstand 1500V AC dielectric strength test for one minute without breakdown Complies with test requirements outlined in ANSI C39 5 1974 for the voltage rating specified Output 4 20mA DC output Note A Test Signal of 40mV to 200mV is available at the output terminals see Drawing 4501 093 it represents the 4 to 20mA output Power An external loop power supply is required 12V DC minimum 50V DC maximum Under no circumstances must the DC supply ever exceed 75 volts peak instantaneously Unit has reverse polarity protection Output Limits typical 3 8mA DC to 26mA DC typical Load Resistance Range Equation R Load Maximum V supply 12V 20mA At 24V supply R Load 0 to 600 ohms Power Supply Effect DC Volts 0 001 of output span per volt
15. librated GENERAL MAINTENANCE The transmitter contains solid state components and requires no maintenance except for periodic cleaning and calibration verification When a failure is suspected a convenient method for identifying a faulty transmitter is to exchange it with a known good unit It is highly recommended that a non functioning transmitter be returned to Acromag for repair since Acromag used tested and burned in parts and in some cases parts that have been selected for characteristics beyond that specified by the manufacturer Further Acromag has automated test equipment that thoroughly checks the performance of each transmitter
16. nt resolution Ambient Temperature Range 13oF to 185oF 25oC to 85oC Ambient Temperature Effect Less than 0 01 of output span per oF 0 018 per oC over ambient transmitter range for Series 250T User s Manual Frequency ___________________________________________________________________________________________ 3 reference test conditions Includes combined effects of zero and span over temperature Load Resistance Effect Less than 0 005 of output span for 100 ohm change Output Ripple Less than 0 5 of maximum output span for inputs from 10 100 of full scale when recommended filter is selected This can be reduced to less than 0 1 by adding a one 1 uf capacitor across the load Bandwidth 3dB at 25 600 Hz typical Response Time Shunt block selection of the filter networks on the PC Board will result in different response times Standard unit is shipped with the 0 4 second response filter To maintain low output ripple for each frequency range use the recommended filter For a step change in the input frequency the nominal response time for a 98 change of the output span is specified below Install shunt blocks per Table below Table Frequency Range Response Time Selection Response Time 98 Frequency Span Range Filter Jumpers Jumper Block J1 shunt 8 0 sec A thru J Pins 1 amp 3 Pins 2 amp 4 5 0 sec C thru J Pins 3 amp 5 Pins 2 amp 4 0 4 sec D thru J Pins 3 amp 5 Pins
17. nusoidal output from a passive magnetic pickup is a typical zero crossing signal A typical TTL output is a non zero crossing type Refer to table 2 on Drawing 4501 095 for proper jumper shunt position 2 Input Frequency Range Select the desired frequency range for the input signal and place the shunt block in the required range position A through J Refer to table 3 on Drawing 4501 095 for proper jumper shunt position Note for best results select the smallest frequency range that will cover the frequency span being monitored 3 Output Ripple Response Time Select the filter for desired results Refer to table 1 of Drawing 4501 095 for proper jumper shunt position Refer to Response Time in the preceding SPECIFICATIONS section which describes the frequency response time combinations that can be achieved while maintaining less than 0 1 output ripple from 10 to 100 of full scale Faster response times may be used when output ripple is not critical Non factory calibrated units have a 0 4 second response time 4 Important Mark the Transmitter s Configuration on the calibration label located on the enclosure Example IN Bipolar Range I 0 to 12 800Hz Filter 3 0 4 seconds Series 250T User s Manual Frequency ___________________________________________________________________________________________ 6 Jumper Configuration Example The following is the jumper configuration for the example below configure y
18. o not push screwdriver blade into the housing more than approximately 0 1 inches while prying it apart Handling of printed circuit boards should only be done at a static free workstation otherwise damage may occur 1 To begin disassembly refer to Drawing 4501 095 place the screwdriver at point A left side of the transmitter While pressing the blade into the seam use a twisting motion to separate the sides slightly Repeat this operation at point B 2 Now that the two pieces have been partially separated use the screwdriver blade to work the left side of the package loose by working around the transmitter and carefully prying the sides further apart Repeat this action until it is easy to remove the left side from the plastic pins holding the pieces together 3 Repeat 1 amp 2 for the right side starting at points C and D CAUTION If the two boards become separated while taking the package apart re align the boards making sure that both headers pins and sockets at locations E and F are aligned and carefully push the boards back together Jumper Configuration Shunt Blocks Shunt blocks are provided to accommodate in field configuration changes In case of misplacement additional shunt blocks may be ordered from the factory When ordering additional shunt blocks refer to Acromag Part Number 1004 332 1 Input Conditioning Selection Determine whether the input signal is a zero crossing or a non zero crossing signal The si
19. our own unit as required for your application A Unipolar Bipolar Bipolar Shunt J1 pins 9 amp 10 B Frequency Range Range I 0 to 12 800Hz Shunt J2 position I C Ripple Response 0 4 sec Shunt J1 pins 3 amp 5 4 amp 6 Transmitter Adjustment Procedure Connect the transmitter as shown in Connection Drawing 4501 093 The input signal source must be adjustable over the entire frequency range 0 25 600 Hz of the transmitter In addition the frequency source must be adjustable and stable to any specific frequency with an accuracy of 0 1 or better Signal amplitude should be set at a level representative of the actual input signal It is recommended that a frequency counter be used to measure input frequency as most dial markings are not accurate The transmitter power supply voltage must be adequate to furnish full scale current to the load plus wire drop plus 12V DC terminal voltage to the transmitter The output current must be measured to 0 1 accuracy or better for proper results The Zero and Span adjustments are accessible on the front panel of the transmitter see Drawing 4501 093 for location The screwdriver blade used to adjust the potentiometers should not be more than 0 1 inch 2 54mm wide Transmitter Calibration Example Model 250T FQ1 XPD1 NCR Input 0 12 800 Hz bipolar input filter 0 4 sec response Output 4 20mA DC 1 The calibration signal amplitude requirements are a function of
20. re installing the right side place the mounting bracket unique to the mounting type you have around the pins at the back of the housing 3 Line up the right side of the housing with the assembly and carefully but firmly press the pieces together B DISPLAY Display Adjustment Procedure If the unit you are calibrating has a display it is calibrated separately from the transmitter The calibration of the transmitter must be verified FIRST see above procedure before verifying the calibration of the display module Refer to Drawing 4501 093 for location of Transmitter s Zero and Span adjustments and the location of the Display s Zero and Span adjustments NOTE The display option is factory configured for a particular customer specified range the Display Zero DZ and Display Span DS adjustments are trim adjustments only Display Calibration Example Model 250T FQ1 XPD1 NCR Input 0 to 12 800Hz Display 0 to 1280 counts x 10 12 800Hz 1 Set the frequency input to 0Hz the Zero point of the transmitter s span Adjust the Display Zero DZ pot of the display module to the zero of the display range 0000 in this example 2 Set the frequency input to 12 800Hz the full scale point of the transmitter s span Adjust the Display Span DS pot of the display module to the correct full scale display reading 1280 x 10 12 800Hz in this example 3 Repeat steps 1 and 2 until the readings converge The display is now ca
21. rom DC power supplies only Power supply voltage is not critical and normally should be from 12 50V DC The supply voltage must not exceed 75 volts even instantaneously The power supply voltage must be adequate to furnish full scale current to the load s plus transmission line drop plus 12V DC terminal voltage to the transmitter Variations in power supply voltage or load resistance have negligible effect on transmitter accuracy Ripple and Noise Power supply ripple at 60Hz 120Hz is reduced at the load by the transmitter The ripple at the load will be 0 01 of span per volt peak to peak of power supply ripple The unit may have up to 0 25 percent of internally generated ripple connect an external luf capacitor across the load to reduce this ripple to less than 0 1 percent if desired 2 Grounding The two wire transmitter in the General Purpose Housing is plastic and does not require an earth ground connection If the transmitter is mounted in a metal housing a ground wire connection is required Connect the ground terminal green screw to a suitable earth ground using suitable wire per applicable codes 3 Input Connect input per Drawing 4501 093 If unit is factory calibrated the calibration label indicates range of input Note The input circuit is electrically isolated from the output power circuit allowing the input to operate up to 250V AC or 354V DC off ground on a continuous basis CALIBRATION A TRANSMITTER This s
22. the Input Conditioning Type selected A Unipolar Threshold 1 5V DC Nominal use a 0 2 0V signal or greater B Bipolar Threshold 0 0V DC Nominal use a 0 2V signal or greater 2 Set the input frequency to 0 Hz Adjust the Zero Z pot until the output reads 4 000mA DC If the output cannot be reduced to 4 000mA turn the Span pot counter clockwise until the output is reduced to the desired value Note If the minimum input is 0 Hz it can be simulated by temporarily disconnecting the signal generator and shorting the input terminals of the transmitter Before going to Step 3 remove the short circuit and connect the signal generator to the input terminals 3 Set the input frequency to 12 800 Hz Adjust the Span S pot until the output reads 20 000mA DC 4 Repeat Steps 2 and 3 above until the readings converge The instrument is now calibrated Several mid point values should also be checked to verify proper operation of the transmitter 5 After the above calibration procedure is complete install the transmitter board assembly back into its case as described in the assembly procedure below Note If the transmitter has the Display Option install it at this time also Assembly Procedure for the 250T Plastic Housing NOTE The Model Serial Number label is on the left side 1 Refer to drawing 4501 095 and line up the left plastic side with the board and terminal assembly Carefully but firmly press the pieces together 2 Befo
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