Lake Shore Model 102 User’s Manual
Service 4-3
4.2.2 Voltage Calibration
To calibrate output current using the DC Ampere Range of a digital
multimeter (DMM), use a DMM with 4-digit resolution or better and a 100 k
Ω
load resistor.
NOTE: If the output current has been reprogrammed to a value other than
the factory preset 10 µA, use a load resistor of the same value as the new
programming resistor. Calibration accuracy is limited to DMM current
measurement accuracy.
1. To open the unit, remove the four rubber feet and four screws from the
bottom of the unit. Gently separate the top half of the enclosure from the
bottom half and front panel.
2. Using the DMM, measure the true resistance of the load resistor.
(If the load is a precision resistor accurate to 0.01%, measuring is
unnecessary.)
3. Place the load resistor between the front panel
CURRENT OUTPUT
terminals.
4. Connect the DMM HI terminal to the
+CURRENT OUTPUT terminal, and
the DMM LO terminal to the
–CURRENT OUTPUT terminal.
5.
Select DC Voltage on the DMM.
6. Adjust
CURRENT ADJ trimpot on Model 102 circuit board until DMM
reads a voltage equal to:
V
load
= (desired current) × (load resistance)
For example, if the desired current is 10 µA and the load resistor
was measured at 100.21 K, adjust the trimpot until the voltage
reads 1.0021 V.
7. Replace top of enclosure, screws, and feet. Resume normal operation.
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