Lake Shore Model 321 Autotuning Temperature Controller User’s Manual
6-12
Service
6. Attach
100
Ω
precision resistor as shown below:
3 (+I)
4 (+V)
2 (V)
1 (I)
R
TEST
100
9
9
6.9.1.3 Input
Calibration
Use the following procedure to perform the input calibration.
1. Place a short across the 100
Ω
resistor.
2. Power on (
l
) instrument.
3. Allow instrument to warm up for at least one hour.
4. With DMM in DC voltage mode, attach test leads between TP2 (–) and TP1 (+).
5. Adjust R29 until DMM voltage reads 2.5000 ±0.0005 VDC.
6. Attach test leads to TP8 (GND1) and TP9 (Vref adj.).
7. Adjust R52 until DMM voltage reads 2.5000 ±0.0001 VDC.
8. Place positive test lead on TP7 (V+Buff).
9. Adjust R27 until DMM voltage reads 0.0000 ±0.0001 VDC.
10. Remove the short from the 100
Ω
resistor.
11. Configure the Model 321 to display units in ohms.
12. Adjust R42 until the display reads exactly 100.00
Ω
.
6.9.1.4
Analog Output Calibration
Use the following procedure to perform the analog output calibration.
1. Attach test leads to TP3 (gnd1) and TP4 (Analog out).
2. Press and hold the Analog Out key until the Model 321 enters the Analog output calibration
mode.
3. Press the Up arrow key until Zero is selected.
4. With the DMM in DC voltage mode, adjust R22 until the voltage is 0.000 ±0.001 VDC.
5. Press the Up arrow key until Span is selected.
6. Adjust R18 until the voltage is 10.000 ±0.001 VDC.
7. Press Escape on the Model 321 to exit the Analog output calibration mode.
8. Set power switch to off (
O
). Disconnect power cord and test resistor.
9. Replace top of enclosure and secure with four screws.
10. Replace back bezel and use 5/64 hex key to tighten two screws attaching bottom panel to unit.
