BCT-2000 Software and BCT-128 and BCT-256 User's Guide - Alber

15.9. Preamp Offset and Gain Calibration1. Calibrate if As-Found readings are not within specification:The current count at +100mV must be within 30 counts of the count at -100mV.2. Power off the BCT, remove the BCT cover, and power up the BCT.3. Locate the I/V/IT board in the BCT. This board has two multiturn pots, RV1 and RV2, onthe rear of the top edge.4. Complete the Preamp Offset and Gain – After Calibration section of the CalibrationRecord as follows:5. On the main menu, click Diagnostics, then click I/V/IT on the drop-down menu.6. Set the DMM to millivolts.7. Connect the DMM to the CS-2000 0 - 200mV jacks.8. Set the Reverse Polarity switch to plus (+) and adjust the CS-2000 for a DMM reading of+100mV.9. Observe, but do not record, the Current Count reading on the I/V/IT dialog box.10. Set the Reverse Polarity switch to minus (-) and adjust the CS-2000 for a DMM readingof -100mV.11. Observe, but do not record, the Current Count reading on the I/V/IT dialog box.12. Adjust RV2 (rear pot) on the I/V/IT board so that the current count at plus polarity iswithin 30 counts of the current count at minus polarity.13. Repeat steps 8 to 12 several times until count between plus and minus does not vary morethan 30 counts. This sets the preamp offset.14. When the counts are within specification, set to +100mV and record the DMM Input andCurrent Count – As Left, then set to -100mV and record the DMM Input and CurrentCount – As Left.15. Set the Reverse Polarity switch to plus (+) and adjust the CS-2000 for a DMM reading of+100mV.16. Adjust RV1 (front pot) on the I/V/IT board for a Current Count of 20001 30 counts onthe I/V/IT dialog box. Record the Current Count under Current Count - As-Left. This setsthe preamp gain.17. Remove the DMM from the CS-2000.18. Close the I/V/IT dialog box.19. After preamp calibration, the overall current and intertiers must be calibrated.65