NPI TEC-B-01 Operating Instructions And System Description Download Page 34

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TEC-B-01 User Manual

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version 1.1

page 34

10. Technical

Data

Modes of Operation
CC: Current

Clamp

mode

VC: Voltage

Clamp

mode

OFF:

Current- and Voltage Clamp disabled, BA amplifier operational

EXT: External

mode

MODE selection: by rotary switch

Summary of Contents for TEC-B-01

Page 1: ...IPTION FOR THE TEC B 01 VOLTAGE CLAMP UNIT FOR BRIDGE AMPLIFIERS VERSION 1 1 npi 2014 npi electronic GmbH Bauhofring 16 D 71732 Tamm Germany Phone 49 0 7141 9730230 Fax 49 0 7141 9730240 support npiel...

Page 2: ...Simple cell model 11 4 1 Cell Model Description 11 4 2 Basic settings 12 4 3 Connections and Operation 13 Checking the Configuration with the Cell Model 13 5 Test and Tuning Procedures 13 5 1 Current...

Page 3: ...e device is to be operated only at 115 230 Volt 60 50 Hz AC Please check for appropriate line voltage before connecting any system to mains Always use a three wire line cord and a mains power plug wit...

Page 4: ...nt electrode connected to the TEC B 01 and potential measurement is performed through the bridge amplifier The active connection of the two amplifiers is indicated by the DUAL LED The bridge amplifier...

Page 5: ...____________________________________________________________________________________________________ __________________________________________________________________________________ version 1 1 page...

Page 6: ...it is necessary to use high GAIN settings but the system becomes unstable and begins to oscillate if the GAIN is set too high 3 Rs COMP potentiometer 10 turn potentiometer to set the amount of series...

Page 7: ...TEC B 01 is equipped with a current source that is connected to the current injecting electrode and performs the current injection This current source has a high impedance floating output Therefore th...

Page 8: ...ay fluctuate around the baseline of 0 mV by some mV With a 1 M resistor as used in the cell model 1 mV corresponds to 1 nA Keeping in mind that the display accuracy of the current is 10 nA in the last...

Page 9: ...firmly connected for linking the TEC B 01 amplifier to the bridge amplifier connector TO TEC B 01 at the rear panel of the bridge amplifier CHASSIS This connector is linked to mains ground green yello...

Page 10: ...nt electrode is connected to the TEC B 01 headstage and the potential electrode to the headstage of the bridge amplifier In two electrode operation current injection is done with the current electrode...

Page 11: ...cell model PEL BNC connector for the potential electrode resistance 1 M REF SUBCLICK subclick SMB connector for the reference electrode optional GND ground connector RM switch for the cell membrane re...

Page 12: ...tings Before using the TEC B 01 always make the basic settings to avoid oscillations Basic settings Turn all controls to low values less than 1 and each symmetrical offset adjustment i e C HEADSTAGE B...

Page 13: ...up condition i e 20 to 30 minutes after turning power on The following test and tuning procedures are necessary for optimal recordings It is recommended first to connect a cell model to the amplifier...

Page 14: ...ls involved tip potential junction potentials etc Warning High voltage Always turn power off when working directly on the current headstage output Put the holding current switch to position 0 0 switch...

Page 15: ...ECTRODE OFFSET 11 potentiometer Note If a cell model is connected the OFFSET controls should read values around 5 otherwise it is likely that the headstages or the amplifier are damaged If microelectr...

Page 16: ...ectrode low pass characteristic due to stray capacities is compensated for by a feedback circuit negative capacity compensation CAPACITY COMPENSATION and a driven shield arrangement for an overview se...

Page 17: ...s not active The POTENTIAL display BA 03X should read 10 mV according to Ohm s law The voltage at PEL 36 should be 100 mV Remember The voltage at PEL is the membrane potential multiplied by 10 Disable...

Page 18: ...0 2 V to COMMAND INPUT 15 The length of the test pulse should be at least 30 ms You should see a potential step of 200 mV amplitude at BA 03X POTENTIAL OUTPUT 36 Note If you expect the POTENTIAL displ...

Page 19: ...des the fastest response to a command step with very little overshoot maximum 4 or 3 the symmetrical optimum SO has the best performance compensating intrinsic disturbance signals but shows a consider...

Page 20: ...the control mode switch to SLOW INTEGRATION to activate the integrator The controller is now in PI mode proportional integral Tune the GAIN again see above Watch the potential output and tune the tim...

Page 21: ...l The critical compensation is achieved when the slow tail of the transient disappears If you see ringing around the slow tail this a sign that the electrodes are not optimally positioned see also cha...

Page 22: ...rane at the other side of the oocyte Thus the voltage controlled by the clamp is different This leads to a capacitive transient with a slow tail see Figure 7 right side Placing the current electrode c...

Page 23: ...e g an oocyte using low resistance electrodes Cm membrane capacity Rm membrane resistance RCEL current electrode resistance RPEL potential electrode resistance RREF reference electrode resistance Rs...

Page 24: ...hearing the membrane potential Remember The membrane potential of the oocyte is strongly dependent on the condition of the oocyte leaky or not the experimental solutions and the membrane proteins chan...

Page 25: ...ellet or Ag AgCl coating of the silver wire in the agar bridge are damaged 3 There is an unwanted GND bridge e g caused by a leaky bath 4 The headstage or the amplifier has an error Solutions 1 Chlori...

Page 26: ...edback systems Froehr 1985 Most voltage clamp systems are composed only of delay elements i e elements which react with a retardation to a change This type of closed loop systems can be optimized easi...

Page 27: ...150 A With this current a cell with a capacity of 100 nF can be depolarized by 100 mV in approximately 100 s which comes close to the theoretically possible speed of response without any detectable d...

Page 28: ...arge voltage activated currents are investigated o Symmetrical Optimum SO uses also the PI controller and has the best performance compensating intrinsic disturbance signals The response to a command...

Page 29: ...ontroller by setting the voltage clamp control mode switch to SLOW Apply adequate test pulses without filtering Adjust the integrator time constant 19 to achieve the overshoot of the selected optimiza...

Page 30: ...current transient is mono exponential and the amplifier can be tuned without ringing around the slow tail of the transient Greeff 2000 Before the experiment make sure that the electrodes are in optim...

Page 31: ...rane several hundred of milliseconds and the sum of small time constants resulting from the microelectrodes and the electronics a few ten microseconds Note Here only the proportional part of the PI co...

Page 32: ...ation circuit Therefore this time constant is always much smaller than the time constant associated with the current electrode The time constants of the operational amplifiers are small and can be neg...

Page 33: ...maximum cable length is 15 20 cm A cable of 0 5 1 5 m has a capacity in the range of 50 200 pF With such a capacity and an electrode resistance of 1 M Te is in the range of 50 200 s and the speed of...

Page 34: ..._______________________ __________________________________________________________________________________ version 1 1 page 34 10 Technical Data Modes of Operation CC Current Clamp mode VC Voltage Cla...

Page 35: ...e 45 A 1 M Current electrode parameter controls Offset compensation ten turn control 500 mV Electrode Resistance Test obtained by application of square current pulses 10 nA display XX X M selected by...

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