ICM Manual - FHC, Inc.
Contents
1. 9 e hd ee e CI 6 o 7 A g a 1 ea Cat 55 70 0 ICM Impedance Conditioning Module Includes ICM Impedance Conditioning Module ICM Accessorv Kit Includes Electrode Conditioning Cable Rubber feet use optional Calibrated Test Loads User manual not shown 1 4 2 ADDITIONAL ITEMS REQUIRED FOR OPERATION The following additional items are ORDERED SEPERATELV A999 3 IMPEDANCE CONDITIONING MODULE 1 ea 66 EL LC XXX Line Cord Country specific see sec 2 1 4 of this manual for catalog number 1 4 3 REPLACEMENT ITEMS Cat 55 70 0 01 Electrode Conditioning Cable Cat 55 70 0 02 Calibrated Test Loads 1 4 4 OPTIONAL ACCESSORIES The following accessories are available 55 11 0 SAF Rack Frame for Stand Alone Modules A999 4 IMPEDANCE CONDITIONING MODULE 1 4 5 SYSTEM CONFIGURATIONS ICM Impedance Conditioning Module Electrode Conditioning Cable Electrode Holder Microelectrode ak WN gt KCI bath or similar with reference wire 1 5 CONCEPTS 1 5 1 TERMINOLOGY Impedance In the field of microelectrodes the impedance value is a reference number that relates to the amount of exposed metal at the tip The classical definition of impedance as the combination of resistance inductance and capacitance of an AC circuit is useful in terms of how the microelectrode test circuit is designed however it is not advisable to focus on within the recording circuit In broa2. Built in adaptive line noise suppression and the driven shield electrode cable provides seamless isolation from external noise sources and minimize stray capacitance artifacts in the measurement signal path The line noise suppressor operates in continuous measurement mode and is particularly effective when performing in vivo impedance measurements Electrode conditioning by the end user has been built into the ICM User adjustable conditioning parameters allow removal of small amounts of insulation from the tip to fine tune electrode impedances that are found to be a little high Settings are manipulated through an intuitive pushbutton and adjustment knob interface All cabling necessary comes in the accessory kit The ICM is a software upgradeable device Its firmware is stored on a FLASH memory that can be re programmed with the latest code version available on our support site www neurocraft com 1 3 OPERATING ENVIRONMENT A999 The ICM Impedance Conditioning module components have been designed to operate in a typical laboratory setup They should be placed on a flat surface that is level and free from contaminants and vibration If the unit is used for in vivo measurement a power isolation unit is recommended for safety 2 IMPEDANCE CONDITIONING MODULE 1 4 INVENTORV 1 4 1 ITEMS DESCRIBED IN THIS MANUAL The following Items are included under the following catalog numbers OR Svstems are ordered from the following ICM
3. When back to the calibration constant selection menu rotate the Value Adjust knob to select a different calibration constant and repeat the previous step The list of available calibration constants include a ADC calibrates the analog to digital converter ADC such that the reading of the input voltage V described in the Theory of Operation section is correct b Vout calibrates the output voltage Va please refer to the model of the measurement circuitry described in the Theory of Operation section c lout calibrates the maximum output current i e the current that will pass through Rg when ICM input is shorted Please note that changing the DAC calibration described below will require a re calibration of lout AC C calibrates the AC coupling capacitor value Cac Shnt calibrates the shunt capacitance Cohnt Cap calibrates the stray capacitance C Ref calibrates the reference Va voltage reading omoa Restoring Factory Calibration 1 2 Press Function button and rotate the knob until you see Settings displayed Press Confirm The display will read Save Rotate the knob until you see Fact Cal displayed Press Confirm again to select restoring the calibration to its factory defaults ICM will prompt the user to confirm restoring the factory calibration by displaying Confirm Press Confirm again to restore the factory calibration Measurement and conditioning related parameters fre
4. circuit is lower due to the smaller input impedance The equivalent impedance of a current generator is very large while the impedance of the circuit shown above is roughly equal to the series resistor R through R4 For illustration purposes we will first consider a simple circuit where we neglect parasitic resistors and capacitors Va Ra vy V V L Z Z R The impedance can be calculated using the following formula ER N Va V where Va is the driving voltage of the divider and V is the voltage measured on the electrode One has to note that by measuring the V4 and V voltages with accurately paired ADC inputs like the two inputs of a dual stereo CODEC no voltage calibration is required for the inputs since the impedance is calculated as a ratio of two voltages that is independent of the way they are expressed Plain numbers A999 6 IMPEDANCE CONDITIONING MODULE resulting from ADC conversion in the range 32768 to 432767 for a 16 bit conversion can be used with no conversion to an actual voltage In order to minimize the measurement errors the resistor Ra will need to have a resistance of the same order of magnitude as the electrode Therefore a number of different resistors R through R will be switched using analog switches or relays In fact the electrode impedance has both a resistive and capacitive component The inductive components can be neglected on the frequency range of interest typically under
5. 0 025 lead acetate results in the deposition of spongy colloidal layer of platinum that increases the tip area effectively reducing the tip impedance On the other hand passing DC or low frequency currents through electrodes immersed in many other electrolytes e g saline results in an increase of the tip impedance due to the deposition of layers of non conductive material or even to the electrode tip electrochemical etching resulting in a reduction of the effective tip area The impedance of the electrode strongly depends on frequency The frequency variation of the impedance using typical values for the model components from Robinson 1968 is show below 10 r T Total Series 7 Shunt 10 L E ee A A A L petits i fej til L L ro six L ae ee E E oa 40 10 10 10 10 v Hz The typical frequency variation of the electrode impedance calculated for R 50kQ Ce 50pF at 1kHz R 713300MQ at 1kHz Rm 1000 and C 100pF The series resistance is composed of Rs Rm Ce and Re The shunt impedance is given by Cs The total electrode impedance as measured by ICM is the series electrode resistance in parallel with the shunt impedance When measuring the electrode impedance at two different frequencies for example 100Hz and 1000Hz with the model parameters used in the above figure one should expect a 5 8 times larger impedance reading at 100Hz compared to the value at 1000Hz Any direct compar
6. 10 kHz Electrodes may have complex models that include several lumped or distributed resistors and capacitors Regardless of the complexity of the electrode model at any given frequency it may be reduced to an equivalent simple circuit containing a resistor and capacitor connected in series or parallel The choice of the series or parallel representation depends on the frequency and ratio between most salient resistive and capacitive elements or even on the investigator s preferences In many situations the parallel circuit is the closest representation of the electrode s more complex model therefore it will be considered the basis of our representation Impedance can be represented as a complex number where the resistive component accounts for the real part and the capacitive reactance for the imaginary part Ce nc alla E n oe Z Re ilo mapei joC R e where 27v and v is the frequency of the signal The parallel circuit can be converted to its series equivalent using the following transformations R R l C C l l S e 3 S e 1 0R C oR C The transformations point to a lower series resistance and a higher series capacitor compared to the parallel values When calculating the electrode impedance one has to compensate for the additional resistances and capacitances in the measurement circuitry For instance the electrode leads may have a negligible resistance compared to the electrode contact resistance
7. ICM Accessorv Kit O A999 IMPEDANCE CONDITIONING MODULE A999 IMPEDANCE CONDITIONING MODULE A999 FHC Providing Instrumentation and Apparatus for Cellular Research Intraoperative Recording and Microneurographv Micro electrodes Micropipettes and Needles to the Neuroscience Community for 30 years microTargeting neuro craft FHC Headquarters 1201 Main Street Bowdoin ME 04287 USA Fax 207 666 8292 E mail fhcinc fh co com WWW fh co com 24 hour technical service 1 207 666 8190 1 800 326 2905 US amp Can FHC Europe TERMOBIT PROD srl 129 Barbu Vacarescu Str Sector 2 Bucharest 020272 Romania L005 18B IMPEDANCE CONDITIONING MODULE Innovation through collaboration Impedance Conditioning Module 55 70 0 ICM Impedance Conditioning Module A999 IMPEDANCE CONDITIONING MODULE TABLE OF CONTENTS Manual A999 Impedance Conditioning Module 55 70 0 ICM 0 Declarations 0 1 Declaration Of Conformitv 0 2 Conditions For Use 0 3 Svmbols Used 1 Operational Manual 1 1 Features 1 2 Description 1 3 Operating Environment 1 4 Inventorv 1 4 1 Items Described In This Manual 1 4 2 Additional Items Required For Operation 1 4 3 Replacement Items 1 4 4 Optional Accessories 1 4 5 System Configurations 1 5 Concepts 1 5 1 Terminology 1 5 2 Design Description 1 6 Technical Summary 1 6 1 Specifications 1 6 2 Controls Connectors 1 6 3 Compatibilities 1 7 Illustrative Procedure 2 Reference Manua
8. It is advised that the electrode impedance is checked even under real recording conditions while inserted into the preparation or in vivo The measured impedance would not only depend on geometry and recording conditions but also on the electrical parameters of the measurement since components in the electrode model discussed above may have non linear voltammetric or frequency characteristics Higher measurement currents or voltages generally result in lower impedance readings Not only that but higher currents may lead to irreversible morphological and electrochemical properties of the electrode 10 IMPEDANCE CONDITIONING MODULE A999 resulting in a change of the electrode impedance In general high measurement currents will cause a permanent drop in the electrode impedance This effect is the basis of electrode conditioning process where high AC currents are used to lower the electrode impedance This is why the ICM factory default on the measurement current or voltage is set to 15 of the full scale and one should use caution with higher output values On the other hand when one applies DC or very low frequency signals to the electrode in most cases electrolytical processes develop at the electrode electrolyte interface that may result in both an increase or a decrease of the impedance depending on the nature of the electrolyte Passing a DC current through an electrode immersed in Kohlrausch s solution 3 PtCl 0 025 N HCI and
9. a high degree of durability has been designed into the Impedance Conditioning Module components care should be taken not to drop them Place all cables and leads where they will not be inadvertently pulled or tangled 0 3 SYMBOLS USED USB This symbol is used to designate a standard USB connection A999 DOC 1 IMPEDANCE CONDITIONING MODULE 1 OPERATIONAL MANUAL 1 1 FEATURES e Fast readout of electrode s impedance resistance or capacitance to two or three digits depending on range e A range of adjustable currents and frequencies allows user to perform electrode conditioning e Provides optional line noise suppression on the measurement signal in noisy environments e Selectable frequency and voltage current allow measurement of complex electrode properties like impedance spectrum when interfaced to an external computer e Intuitive knob and pushbutton control of functionality e All necessary cabling included in accessory kit e Compact modular desktop or rack mountable 1 2 DESCRIPTION The ICM Impedance Conditioning Module gives the researcher accurate information about the integrity and electrical characteristics of metal microelectrodes User selectable readings of impedance resistance and capacitance provide a wider range of microelectrode information than has been previously available The DSP digital signal processor technology executes complex math algorithms providing accurate readings to two significant digits
10. a memory area prior to measurement For instance for a 1 kHz signal frequency the table will contain 48 samples The measurement sequence begins with the generation of the output waveform for about 0 2 seconds rounded to the nearest integer number of waveform periods During this interval no readings of the input waveform are made the output is allowed to settle to a stationary value After this interval elapses the input waveform is continuously digitized with the same rate at which it is synthesized and values are stored ina buffer In fact for every cycle of the output waveform the data is averaged into the same buffer having a length corresponding to the number of samples for a waveform period Simultaneously the driving voltage is digitized and average in the same way in a separate buffer to be used as the reference signal The data is acquired for the user selected measurement time rounded to the nearest multiple of the waveform period When the measurement is complete ICM calculates the amplitude of the reference and input and the phase difference by performing a complex Fourier transform of the signal at the selected waveform frequency for the reference and input waveforms The phase angle is calculated based on the ratio between the real and imaginary parts of the Fourier transform Using the Fourier method for calculating the phase angle proved to be much less sensitive to noise as compared to other methods like detecting the zero c
11. but they definitely have a significant stray capacitance Cs This capacitance is shunting the electrode signal to ground particularly at high frequencies This stray capacitance C is included along with other components that will be described in the next paragraphs in the equivalent measurement circuit shown below T The analog circuitry that reads V has an input impedance composed of a resistor in parallel with a capacitor whose resistive component Rin can be neglected in most instances 107 Q while its capacitance can be included in the Cstray value A999 7 IMPEDANCE CONDITIONING MODULE In addition to that the resistor in series with the driving voltage has a parallel capacitance tvpicallv in the sub pF range but that cannot be neglected in certain instances In order to have a null net current through the electrode to prevent electrolytic processes that would etch the tip an AC coupling capacitor C is inserted in series with the output Its contribution cannot be neglected at low frequencies for low electrode impedances lt 10 kQ In order to simplify the calculations that will return the electrode impedance value we will represent the various resistive and capacitive components as complex impedances as shown below n e ha i STR Oa TATI ET The output voltage will be Z Za II Zs V l Z Za ll Z Zy After a series of elementary calculations one obtains the complex value of th
12. CHNICAL SUMMARY 1 6 1 SPECIFICATIONS ICM A999 Measurement Accuracy 5 actual Displayed to 2 3 digits depending on range Measurement Applied Voltage Adjustable 10 100 of 1 75Vpp sine wave Default is 20 Measurement Frequency Adjustable from 50Hz to 4kHz Impedance Range 1kQ to 100MQ Conditioning Voltage Range Adjustable 10 100 of 3 5Vpp sine wave Default is 100 Conditioning Current Frequency Adjustable from 50Hz to 4kHz Display 8 characters 1cm height red Power Requirements 100 240 VAC 50 60Hz Dimensions Height 13cm 5 22 Width 10cm 4 20 Length 25cm 9 75 Weight 1 48 Kg 3 26 Ibs Mounting Options Tabletop 4 rubber feet prevent sliding Rack mountable with SAF Rack Frame Cat 55 11 0 Available separately Computer Interface High speed USB 2 0 backwards full speed USB 1 1 compatible Computer needed for FLASH upgrade only 12 IMPEDANCE CONDITIONING MODULE 1 6 2 CONTROLS CONNECTORS neuro craft Function Confirm ZIRIC Value Adjust Display ICM Front Panel Value Display 8 character alphanumeric display of modes of operation user menu options and measured values Controls ICM Front Panel Function Toggle pushbutton for scrolling through functionality menu see below for menu hierarchy Confirm Toggle pushbutton for confirming selection of functionality menu parameters Z R C Toggle pushbutton for scrolling through last measurement values for Impedance Z Resi
13. Dre EC Declaration of Conrormity we FHC Europe TERMOBIT PROD srl of 129 Barbu Vacarescu Str Sector 2 Bucharest 020272 Romania declare that Equipment ICM Impedance Conditioning Module Model Catalog No s 55 70 0 Serial Number has been designed and manufactured to the following specifications IEC61326 Electrical Equipment for Measurement Control and Laboratory Uses I hereby declare that the equipment named above has been designed to comply with the relevant sections of the above referenced specifications The unit complies with all essential requirements of the M Fred 2008 01 16 Signed by cH 92 Name Frederick Haer 05 00 Position President FHC Done at FHC Inc 1201 Main Street Bowdoin ME 04287 USA Phone 1207 666 8190 Fax 207 666 8292 E mail fhcinc fh co com Website http www fh co com Date A999 DOC A999 IMPEDANCE CONDITIONING MODULE QUALITV INSPECTION SUMMARV We have made every effort to manufacture this instrument to the highest quality standards All assemblies have been thoroughly tested and inspected at the factory as follows Initial Assembly Inspection O Initial QC Inspection Calibration O 24 Hour Burn In O Final Performance Inspection O Packaging Inspection Initials Date Items included with any catalog number may be labeled and packaged separately in shipping carton Description Quantity Checked Cat 55 70 0 ICM Impedance Conditioning Module Containing ICM U
14. ODULE 2 Measure Mode Frequency Testing This section will include testing of frequency settings Basically the test is to set the parameter and verify that what we measure with an O Scope is the same as what we set it to We will use a 10K resistor for this test a Select Measure Mode Like in step 1 above select the Measurement Menu b Configure Duration Set the duration to a longer time to allow for measurement of the frequency To set the Duration rotate the value adjust knob for Duration menu Press the confirm button to select this menu Rotate the value adjust knob for a long duration between 6000ms to 9999ms enough to perform frequency measurement with your O Scope c Configure Frequency Rotate the value adjust knob for Frequency menu Press the confirm button to select this menu Rotate the knob for each of the frequencies to test listed below remember to press the confirm button to accept the new frequency d Using an O Scope measure the signal frequency across a 10K resistor placed between the black amp red terminal of the ICM cable Record the frequency measure for each frequency to test in the table below repeat steps 2c amp 2d for each frequency to measure Frequency to Test Expected Measured 100 Hz 5 1K Hz 5 4K Hz 5 3 Measure Mode Output Voltage Testing This section will include testing of Measure output volta
15. TIONING MODULE 4 Press the Activate button once The display will read Meas while processing and then display the impedance Z measurement default or the last measurement type used impedance resistance or capacitance Pressing the Z R C button toggles through the last measured values of impedance Z resistance R or capacitance C If the value is out of range or the measurement is presumed inaccurate the display will blink For instance when reading a 100k impedance on a manually selected the range of 10 MQ the measured impedance will still be displayed and may be close to the actual one but the display will be blinking to indicate that the range is inappropriate for the measured impedance value and the accuracy of the measurement may be poor Setting Conditioning Parameters 1 3 4 Press Function button If the unit was last left in manual condition mode display will read Cond Press Confirm button to access conditioning parameters If a different mode is displayed Measure Plating etc rotate Value Adjust knob until display reads Cond then press Confirm button to access conditioning parameters Once the Confirm button is pressed the last parameter viewed will be displayed Rotate Value Adjust knob to toggle through the parameters Frequency Duration Output Press the Confirm button to access the setting Use the Value Adjust knob to dial in the setting press the Con
16. Z Check Unit is now ready for use 5 Route cable so it can t be inadvertently pulled or tangled and connect the black pin to the electrode the red pin to the bath and the green clip to common ground If using differential mode connect green clip to reference electrode AON 2 3 FUNCTIONAL CHECKOUT Functional Checkout 1 Measure Mode Impedance Measurement Verify the accuracy of Impedance Measurement by performing the following steps below a Selecting Measure Mode Rotate the value adjust knob for Measure menu Press confirm key to enter menu b Configure Range While in the Measure menu rotate the value adjust knob for Range Press confirm key to enter Range menu While in the Range menu rotate the value adjust knob for first range to test Press confirm key to accept setting c Measure Impedance Place the first resistor to be tested matching the range set in the above step Record in the table below the value of the resistors Z amp R value the Z amp R values are toggled by the Z R C switch You will use a precision 1 tol resistors for values of 10K 100K 1Meg 8 10Meg Remember to repeat steps b amp c for each range tested Value Range Expected Measure 10K Value 5 100K Value 5 1M Value 5 10M Value 5 Auto Range Expected Measure 10M Value 5 A999 19 IMPEDANCE CONDITIONING M
17. ate the knob until Cancel is displayed and press Confirm or press Function button Restoring Settings 1 2 A999 Press Function button and rotate the knob until you see Settings displayed Press Confirm The display will read Save Rotate the knob until you see Defaults displayed Press Confirm again to select restoring the settings to their factory defaults ICM will prompt the user to confirm restoring the current settings to their defaults by displaying Confirm Press Confirm again to restore the settings All measurement and conditioning related parameters are reset to their factory defaults The calibration is not reset to its factory default To cancel saving rotate the knob until Cancel is displayed and press Confirm or press Function button 23 IMPEDANCE CONDITIONING MODULE Re calibrating ICM 1 2 ok ow Press Function button and rotate the knob until you see Measure displayed Press confirm to select adjusting measurement parameters Rotate the knob until you see Range displayed Press Confirm to select the measurement range you would like to re calibrate Rotate the knob to toggle through the available ranges Press Confirm when the desired range is displayed Press Function to exit the measurement menu and go back to the top level menu Connect a known impedance at the ICM input then press Activate to perform a measurement Press Function button an
18. d rotate the knob until you see Calibration displayed Press Confirm The display will read Cal ADC Pressing Confirm again will select calibration of the ICM analog to digital ADC converter and will display the last measured Z R C value Rotate the ValueAdjust knob to change the calibration of the ADC ICM will re calculate the Z R C value based on the updated ADC calibration and display the result Rotate the knob until the ICM indication will match the value of the impedance connected at the input You can press Activate button at any time for performing a new measurement instead of using the last measured values You can press Confirm again to accept the change and save the value to NVRAM or Function to reject it Canceling the change will not restore the original value of the calibration constant you will need to cycle the power to restore the original calibration Please note that calculated Z R C values are dependent not only on one calibration constant but on all the constants for a particular range Making the ICM indication match the value by adjusting only one calibration constant at a particular frequency for a particular resistive or capacitive load will not guarantee that the ICM will perform a correct measurement at any frequency for all type of loads The ICM calibration is a multi step process that is beyond the scope of this manual Please contact a FHC technical representative if you think ICM requires a re calibration
19. d terms high impedance produces a more focused recording field that is useful for single unit recording The trade off for this is that as the signal is amplified so is the noise A low impedance electrode is generally quieter but records from a wider number of neurons without much inherent selectivity and low amplitude The impedance value should be looked at as a reference point to duplicate recording situations that have proven to provide reliable data quality See section 1 5 3 for a wider discussion of impedance A999 5 IMPEDANCE CONDITIONING MODULE 1 5 2 DESIGN DESCRIPTION The design is based on the APM hardware design which contains a 32 bit Digital Signal Processor DSP allowing complex processing of data Analog circuitry and signal conditioning is reduced to a minimum several signal conditioning tasks are being implemented as numerical algorithms that operate on the digitized data ADC DAC Alno Z 4 Electrode Theory of operation Since the data acquisition is driven by a DSP that can perform complex mathematical operations there s no real need for a constant current generator that would provide a linear relationship between impedance and output voltage Instead a constant voltage generator can be used and the measurement circuit can be a plain voltage divider with the electrode as one branch In fact the constant voltage solution is less sensitive to noise since the amount of noise picked by the measurement
20. e The Differential Mode setting is found in the Measurement Mode menu selection The Diff Mode allows alternate grounding reference connections i By default the Diff Mode is set to off Change this to on and press the confirm key Place a 10K 1 resistor between the red and black leads of the electrode measurement cable ii Next while in Measurement Mode press the activate button You will now see an impedance measurement different than an expected 10K due to the internal removal of ground reference via the relay controlled by Diff Mode iii Connect the Ground to the Red lead of the ICM cable with 10K resistor still between the Red and Black lead Press the activate button and should get an expected 10K measurement Set the Diff Mode back to off setting Did Diff Mode testing pass b Saving Configuration Settings Test This section will test the retention of parameter setting to NV Flash Ram All that is required is to set only a few settings to determine that they have been retained i Change any parameter setting from within Measure or Cond modes Remember to press the Confirm button to accept any changes ii Select the Settings Menu and press confirm at the Save prompt iii Turn off the ICM then back on after 10 sec iv Return to the Measure or Cond mode where you made changes and note that your change is still there Did Saving Configuration Settings pass 8 Test Complete You have completed the functi
21. e extrusions and are held in place when the back panel is secured into the extrusion All modules are 9 75 in depth Tvpe 2 Module Tvpe 4 Module Tvpe 6 Module 2 1 2 MOUNTING All stand alone modules are completely encased and can be used without further mounting or hardware Provided rubber feet may be used to protect surfaces from scratching However it may be suitable to group modules and we have made provision for several configurations The SAF Rack Frame for Stand Alone Modules cat 55 1 1 0 will hold up to eight Type 2 modules four Type 4 modules or two Type 6 modules and 2 ea Type 2 Dress Panels cat 55 11 1 use optional while occupying only 3 rack units 5 25 vertically on a standard 19 instrument rack Several combinations are available for all of the neuroCraft series stand alone modules For example an SAF frame could accommodate 3 Type 2 1 Type 4 and 1 Type 6 within its 16 of horizontal rack space SAF Rack Frame For Stand Alone Modules Shown with a neuroCraft Type 2 Module Dress Panels for SAF Ordered Separately e 55 11 1 Type 2 Dress Panel A999 17 IMPEDANCE CONDITIONING MODULE 2 1 3 INSPECTION FHC Modules are factory checked and calibrated but should be carefully inspected upon receipt before using or activating power If any exterior damage to the shipping carton is noted the instrument s should be inspected for obvious physical damage The contents of each package should be physically c
22. e impedance as Z Ze 1 ov VZ Z S One has to note that due to the capacitive component in the electrode and measurement circuitry the voltage V will have a different phase than the driving voltage Va and can be represented as a complex number V V cos j V sin 9 This phase difference p can be calculated by measuring the delay t between the zero crossing of V relative to the zero crossing of Va O 360 in degrees where T is the period of the driving signal 1 ms for a 1000Hz wave The driving voltage Va is taken as reference and will only have a real component For the simple parallel model the complex impedance will be 1 1 joC Z R and the real and imaginary parts of the inverse of the complex impedance will provide us with the following values for Re and Cs E zi __Im Z RZ lef A999 8 IMPEDANCE CONDITIONING MODULE While the measured voltages V and Va require no calibration in order to provide an accurate measurement the other parameters in the impedance formula Zs Za Zac Or rather their underlying Cstray Ra Cshnt Cac are part of the ICM calibration constants set However in order to provide a controlled driving signal Va will be calibrated as well in ICM The driving signal Va is synthesized point by point using the CODEC DAC operating at a sample frequency of up to 48 kHz A table with the points for a single sine wave period is pre calculated in
23. ectric double layer formed around the electrode tip due to electrochemical processes is the leakage resistance due to charge carriers crossing the electric double layer m is the resistance of the metallic portion of the microelectrode is the accumulated shunt capacitance to ground from the tip to the input of the amplifier This includes the capacitance of the insulation as well as the capacitance of the wires and connectors leading from the electrode to the preamplifier ao OD DO DW D D ao These parameters should not be considered constant they depend on many other factors and particularly on the signal frequency For instance both the resistance and capacitance of the double layer vary roughly as Jo Gesteland et al 1959 The double layer capacitance has been estimated to be in most common situations anywhere between 0 18 and 1 0 picofarads per square micrometer of exposed metal tip pF um at a frequency of 1 kHz For a tip of 100 UM tvpical of an electrode having a few MQ impedance at 1 kHz the capacitance would be between 18 pF and 100 pF at 1 kHz and roughiv 3 times larger at 100 Hz The spreading resistance of the saline bath is a function of the exposed tip area and geometry and can be anywhere between a few hundred ohms and tens of KQ The shunt capacitance of a typical tungsten electrode immersed for a few centimeters in saline can be as high as 200 pF This corresponds to a shunt impedance of nearly 0 8 MQ at 1 kHz F
24. firm button to apply the new setting Display will return to the parameter menu Press the Activate button once to return to the main display or wait 5 seconds Conditioning Microelectrodes 1 Set up and measure electrode impedance 2 3 Press the Activate button once The display will read Cond while processing through a condition Press Function button and set the manual conditioning parameters as above cycle followed by a measurement cycle and then display the new impedance Z measurement Pressing the Z R C button toggles through the last measured values of impedance Z resistance R or capacitance C indicated by the third display digit Continue conditioning by repeated pressings of the Activate button To change the parameters after any cycle press the Function button and continue as described above Saving Settings 1 2 Press Function button and rotate the knob until you see Settings displayed Press Confirm The display will read Save Press Confirm again to select saving the settings or rotate the knob to select a different subfunction restoring settings or factory calibration When save is selected ICM will prompt the user to confirm saving the current settings as power up defaults by displaying Confirm Press Confirm again to save the settings to the non volatile memory NVRAM All measurement and conditioning related parameters are saved to NVRAM To cancel saving rot
25. ge settings Basically the test is to set the parameter and verify that what we measure with an O Scope is the same as what we set it to We will use a 10K resistor for this test a Select Measure Mode Like in step 1 above select the Measurement Menu b Configure Output Voltage Rotate the value adjust knob for Output menu Press the confirm button to select this menu Rotate the knob for each of the Output Voltage to test listed below remember to press the confirm button to accept the new Output Voltage setting c Place a 10K resistor between the black amp red terminal of the ICM cable Using an O Scope measure the signal output voltage across the resistor with the ground lead of the scope on the red electrode lead and the scope probe to the black electrode lead Record the output voltage measure for each setting to test in the table below Output Setting Expected Measured Vpp 100 1 4 1 7 50 of 100 10 1x 100 4 Measure Mode Duration Testing This section will include testing of Measure duration settings Basically the test is to set the parameter and verify that wnat we measure with an O Scope is the same as what we set it to We will use a 10K resistor for this test a Select Measure Mode Like in step 1 above select the Measurement Menu b Configure Duration setting Rotate the value adjust knob for Duration menu Press the confirm butto
26. hecked against the inventory list sec 1 3 to determine shortages or errors in inventory 2 1 4 POWER CONNECTIONS All of the stand alone modules in the neuro craft series are powered by an internal universal power supply that accepts inputs of 85 265VAC 50 60Hz An international pattern Line Cord not shown is ordered separately and is specified by country per the catalog number See table below for catalog numbers 66 EL LC AUS Australia 66 EL LC CH China 66 EL LC DAN Denmark 66 EL LC EURO Europe 66 EL LC 5 ISR Israel 66 EL LC 5 ITA Italy 66 EL LC JA Japan 66 EL LC SAF South Africa 66 EL LC SWI Switzerland 66 EL LC UK United Kingdom 66 EL LC USA North America 2 1 5 WARRANTY All FHC products are unconditionally guaranteed against defects in workmanship for one year from date of shipment as long as they have been exposed to normal and proper use Although the one year warranty may have expired please contact our Service Department before attempting any repairs or alterations Many of these repairs will still be performed at the factory at no charge to the customer 2 1 6 POLICIES 1 TECHNICAL SUPPORT It is our policy to provide our customers with the most comprehensive technical support in the industry If any questions arise or problems occur we encourage you to call or write and we promise to promptly and comprehensively respond to your requirements 2 TRADE UP POLICY It is our policy to offer customers trade
27. her manufacturers Since the circuitry performing the measurement is likely to be different than that used in the manufacturing of the microelectrodes a different value may be obtained than provided by the manufacturer 1 7 ILLUSTRATIVE PROCEDURE Measuring Impedance Resistance Capacitance 1 Connect leads Black Electrode Red Reference Green Common ground 2 Lower electrode tip in electrolyte solution approx 1mm 3 Press the Activate button once The display will read Meas while processing and then display the impedance Z measurement default or the last measurement type used impedance equivalent resistance or equivalent capacitance 4 Pressing the Z R C button toggles through the last measured values of impedance Z resistance R or capacitance C Conditioning Microelectrodes 1 Set up cable and immerse electrode 2 Press the Function button to display the currently selected function and rotate the Value Adjust to toggle through the available functions Meas Cond etc until Cond is displayed Press Confirm to select conditioning mode and adjust its parameters frequency duration output current The display will switch to Freq frequency which is the first conditioning parameter 3 Rotate the Value Adjust knob if you want to select a different conditioning parameter 4 Press Confirm to display the current parameter value or change it To cha
28. ison between the measured electrode impedance in a lab setting and the nominal impedance claimed by the electrode manufacturer must at least take into account the frequency of the signal and for high impedance electrodes where the shunt capacitance is significant the immersion depth In this latter case the stray capacitance of the measurement leads may be significant While the ICM implements guarded shields and digitally compensates for the stray capacitance any additional wires or connectors may add to the stray capacitance and influence the impedance reading As the factory measurement conditions may be different from vendor to vendor any comparison of electrode impedances across vendors must be made taking into account these differences The phenomena taking place while recording through metal microelectrodes are so complex that Robinson concludes that description of the elements of 11 IMPEDANCE CONDITIONING MODULE microelectrode recording makes it possible to understand however crudelv and approximately which elements are important which are unimportant Unfortunately knowledge of these qualities does not permit one to tell in detail how a given electrode will perform in brain tissue ICM attempts to provide investigators a tool that would give a more accurate indication of various electrode components values for evaluation and better understanding of the electrode properties and their performance for recording 1 6 TE
29. l 2 1 Reference Information 2 1 1 Packaging 2 1 2 Mounting 2 1 3 Inspection 2 1 4 Power Connections 2 1 5 Warranty 2 1 6 Policies 2 1 7 Service 2 2 Installation 2 3 Functional Checkout 2 3 1 Calibration 2 4 Operational Information 2 5 Scheduled Maintenance A999 IMPEDANCE CONDITIONING MODULE A999 IMPEDANCE CONDITIONING MODULE 0 2 CONDITIONS FOR USE Intended Use The Impedance Conditioning Module is used to measure the values of impedance resistance and capacitance in microelectrodes Conditioning modes are intended to fine tune the impedance value of metal microelectrodes Warnings The Impedance Conditioning Module components should not be disassembled bevond their major assemblies Any disassembly beyond this may affect function and calibration If repair is required please contact FHC at 207 666 8190 for evaluation and to secure a return authorization number if necessary Storage Precautions Store at normal room temperatures between 34 C 29 F and 57 C 135 F Do not expose to temperatures below 39 C 29 F or greater than 70 C 158 F or a relative humidity of less than 10 or more than 100 including condensation or an atmospheric pressure less than 500hPa or greater than 1060hPa for long term storage Sterilization None of the Impedance Conditioning Module components are designed for sterilization Any attempt to sterilize them may result in malfunction or component failure Handling While
30. n to select this menu Rotate the knob for each of the Durations to test listed A999 20 IMPEDANCE CONDITIONING MODULE below remember to press the confirm button to accept the new frequencv c Measure the time from the start to end of a measurement cycle using the O Scope Set the scope to a time base setting to capture the entire time envelope Duration Setting Expected Measured 4000 ms 25 2000 ms 25 1000 ms 25 5 Condition Mode Signal Generation Testing Verify that the signal frequency amplitude amp duration is different between the Conditioning Mode and Measurement Mode Note Condition mode exercises two modes of operation conditioning and measurement Conditioning mode remains until it s duration time has expired before the ICM enters Measurement mode Test Method a Place a 10K resistor across the leads of the ICM cable b Connect an O Scope across the 10K resistor like that of other measurements mentioned above c Select Condition Mode from main menu level Press the confirm button to enter Condition Menu d Set the Condition Mode parms as Frequency 2K hz Duration 4000ms Range 10K Output 100 e Set the Measure Mode parms as Frequency 1K hz Duration 2000ms Range 10K Output 20 f Set ICM for Condition Mode and with the scope ready for measurements press the ICM s Activate Button Did you notices a difference betwee
31. n waveforms between the condition mode and measurement modes You should have witness a change in the waveform frequency output voltage amplitude and duration 6 Condition Mode Output Voltage Testing This section will include testing of Condition output voltage settings Basically the test is to set the parm and verify that what we measure with an O Scope is the same as what we set it to We will use a 10K resistor for this test a Select Condition Mode Like in step 5c above select the Condition Menu b Configure Output Voltage Rotate the value adjust knob for Output menu Press the confirm button to select this menu Rotate the knob for each of the Output Voltage to test listed below remember to press the confirm button to accept the new frequency c Place a 10K resistor between the black amp red terminal of the ICM cable Using an O Scope measure the signal output voltage across the resistor with the ground lead of the scope on the red electrode lead and the scope probe to the black electrode lead Record the output voltage measure for each setting to test in the table below Output Setting Expected sinewave Measured Vpp 100 3 00 3 6 50 1 5 1 88 10 300mV 368mV 7 Misc Parameter Testing This section will test the remain parameter setting and it s function Ability to retain settings in memory A999 21 IMPEDANCE CONDITIONING MODULE a Diff Mod
32. nge the current value turn the Value Adjust knob When done press Confirm to accept the displayed value For instance when adjusting the frequency the ICM with briefly display Freq Set and will then go back to the parameter selection menu displaying Freq To cancel the change press Function The display will switch back to Freq 5 When back in the parameters selection menu rotate the Value Adjust knob to select a different parameter for the conditioning duration output then use the same procedure as described at previous step for the adjustment of the parameter value A999 15 IMPEDANCE CONDITIONING MODULE 6 Press the Activate button once The displav will read Cond while processing and then will perform an impedance measurement and displav the impedance resistance or capacitance Z R or C depending on the selected displav mode 7 Follow steps 3 4 to make anv changes to the conditioning settings 8 Press the Activate button to perform further conditioning cvcles 2 REFERENCE MANUAL 2 1 REFERENCE INFORMATION The stand alone modules of the neuroCraft series instruments are packaged in metal cases which consist of standard 5 25 high front panels Front panel widths are specified as Type 2 modules 2 05 actual Type 4 modules 4 15 actual and Type 6 modules 6 25 actual Front panels are mounted on extruded top and bottom panels Flat side panels slide into slots in th
33. onal check out of the ICM Please remember to reset configuration change A quick method to reset configuration changes is to turn the ICM off for 10 Sec then back on Note Configuration changes are saved only if you select Settings then save them For the purpose of functional testing we did not save any of the settings 2 4 OPERATIONAL INFORMATION Setting Measurement Parameters 1 Press Function button If the unit was last left in measurement mode display will read Measure Press Confirm button to access measurement parameters If a different function is displayed rotate Value Adjust knob until display reads Measure then press Confirm button to access measurement parameters 2 Once the Confirm button is pressed the last parameter viewed will be displayed Rotate Value Adjust knob to toggle through the parameters Frequency Duration etc Press the Confirm button to access the setting 3 Use the Value Adjust knob to dial in the setting press the Confirm button to apply the new setting Display will return to the parameter selection menu 4 Press the Function button once to return to the main display Measuring Impedance Resistance Capacitance 1 Connect leads Black Electrode Red Reference Green Common ground 2 Lower electrode tip in electrolyte solution approx 1mm 3 Confirm that unit is in Measurement mode A Z R Or C will be displayed in the leftmost digit A999 22 IMPEDANCE CONDI
34. or long electrodes used for reaching deep brain structures Cs may become particularly important This shunt impedance places a limit on the usable range of electrode impedances While some investigators believe that higher electrode series impedance the sum of Rs Rm and impedance of parallel group C and Re provides better results which is true in terms of achieving better isolation of individual neurons one should keep in mind that this leads to a stronger attenuation of the signal due to the higher electrode shunt impedance ratio In other words in the previous numeric example it won t be particularly useful to use electrodes having an impedance much larger than the shunt impedance i e 0 8 MQ As a rule of thumb the electrode series impedance should not exceed twice the shunt impedance or the signal will be greatly attenuated It is also important that the electrode impedance is measured in conditions similar to those that will be used during actual recordings that is immerse the electrodes in saline for the same depth they will be inserted in the tissue or tissue and guide tube In fact one can measure the electrode impedance with the tip barely making contact with the saline bath measurement that would give an indication of the electrode series resistance and another measurement with it immersed into saline for a depth matching the recording conditions in which case one could figure out what is the contribution of the shunt capacitance
35. quency duration etc will not be affected To cancel restoring rotate the knob until Cancel is displayed and press Confirm or press Function button Continuous mode 1 2 A999 Press Function button and rotate the knob until you see Meas or Cond displayed Press Confirm Rotate the knob until you see Duration Press Confirm again to select adjusting the measurement or conditioning duration and rotate the knob to select measurement duration of less than 200ms When turning the knob past the minimum 200ms value Cont will be displayed Press Confirm again to select the continuous measurement conditioning mode In this mode the measurement will not have a fixed duration but will be performed continuously as long as the 24 IMPEDANCE CONDITIONING MODULE Activate button is held down During the measurement the Z R C value will be continuousiv updated until the Activate button is released In continuous mode the line noise filter is active In the fixed duration mode the filter cannot be activated since it requires a continuous measurement in order to learn a replica of the line noise and subtract it from the signal Please note that an extended measurement time particularly when using a high output current may result in a decrease of the electrode impedance 2 5 SCHEDULED MAINTENANCE A yearly performance of the Functional Checkout in section 2 3 should be performed to ensure function and calib
36. ration If the unit fails any part of this functional test contact the FHC Repair Department at 207 666 8190 REFERENCES Robinson D A The electrical properties of metal microelectrodes Proc of the IEEE 56 Nr 6 1065 1071 1968 Gesteland R C Howland B Lettvin J Y and Pitts W H Comments on microelectrodes Proc IRE vol 47 pp 1856 1862 1959 A999 25 IMPEDANCE CONDITIONING MODULE
37. rossing time The phase o input voltage amplitude IVI and driving voltage amplitude Val are then used in the equations described above for calculating and displaying the impedance Z and the R and C values for the basic parallel equivalent circuit 1 5 3 A REVIEW OF MICROELECTRODE PROPERTIES When one chooses the measurement parameters the complex properties of microelectrodes should be kept in mind The electrode impedance greatly varies with the frequency and amplitude of the measurement signal For instance metal microelectrodes are modeled by complex circuits which can be approximated with a simple parallel or series circuit with a particular resistance and capacitance over a limited frequency range only Robinson Robinson 1968 introduces the equivalent circuit of an electrode as shown below Ce Rs en Electrode Tip To Preamplifier A999 9 IMPEDANCE CONDITIONING MODULE A999 An abbreviated description of the correspondence between various electrical components and parameters and the phvsical structures and values would be as follows e is the potential created by a neuron at the location at the electrode tip this potential has the value that would be created by the neuron in the absence of the electrode the electrode may be in fact perturbing the actual potential is the so called spreading resistance of the saline bath between the electrode tip and the null isopotential line is the capacitance of the el
38. stance R and Capacitance Value Adjust Turn knob used to toggle through parameters in the functionality menu see below for menu hierarchy and to adjust the value of those parameters Any change affected by this knob does not become active until the Confirm button is pressed Activate Green pushbutton for activating the measurement or conditioning cycle Functionality Menu Hierarchy Measure Frequency 50 4000Hz Duration 200 20000ms A999 13 IMPEDANCE CONDITIONING MODULE Range 10k 100k 1M 10M Auto Differential On Off Output 10 100 output voltage Filter On Off Conditioning Frequency 50 4000Hz Duration 200 20000ms Range 10k 100k 1M 10M Auto Output 10 100 output voltage Calibrate ADC 0 100M DAC 0 100M Settings Default Save Fact Cal Connections ICM Front Panel Electrode 6 pin DIN socket for interfacing the Electrode Conditioning Cable 17208 POWER 120Vac 240Vac 50 60 Hz AQ e e Mero A999 14 IMPEDANCE CONDITIONING MODULE fu Controls ICM Rear Panel O i Rocker switch used to activate power Connections ICM Rear Panel Power 3 prong inlet for interfacing line cord to internal universal power supply USB High speed USB 2 0 port for interfacing with a host computer Custom applications only 1 6 3 COMPATIBILITIES The ICM Impedance Conditioning Module will perform measurement and conditioning on microelectrodes offered by ot
39. up ability as new and or expanded capabilities for their instruments are announced In many cases full credit will be given In general we will allow 100 credit for two years and depreciate 20 per year thereafter Please contact our Marketing Department for information relating to your particular situation 2 1 7 SERVICE Should service be required please contact our Service Department for a return authorization number and instructions 207 666 8190 Please have the model and serial number on hand Both are located A999 18 IMPEDANCE CONDITIONING MODULE on the back panel Carefully pack the instrument before returning Please include a note indicating 1 The model number and purchase date of the instrument 2 The person to contact if questions arise 3 The symptoms indicating that repair is necessary If the instrument is not covered by the warranty a quotation will be forwarded to the sender detailing the repairs necessary and charges before repair is begun 2 2 INSTALLATION 1 Attach rubber feet to bottom corners of the ICM if mounting on a desktop If rack mounting in the SAF Rack Frame install the device and tighten the front panel thumbscrew before plugging in any cabling Plug the line cord into the power outlet on the back panel Plug the electrode cable into the jack on the front panel Power up the unit It will go through a Wait USB routine for applications requiring USB and then the display will read
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