Chapter 7: Maintenance
4. Sensing level and range adjustement (refer to figure 7.11)
a) Replace the cable connected to J8 (4) with the 100±1 Ω resistor. Note:
the precision (gold band on the resistor) is important. Connect one side of
the resistor to pins 1 and 2, the other side to pins 3 and 4.
b) Measure the voltage on Zn3/R10 (3): the value should be - V = 1.22 to
1.25V.
c) Measure the voltage at the intersection of R19/R35 (5): the value should
be V=100mV, adjustable with the P1 (2)) knob.
Note: If the range is too small, replace the resistor R1 (1) = 1.3kΩ with
1.4kΩ.
d) Set the selector (9) to display Real
◦
C.
e) Adjust the trimmer P6 (6) in order to obtain the value of 000
◦
C on the
screen (8).
f) Vary the Temperature Reference by using the Set Temperature 5 turns
knob (7) located on the front panel. The range displayed should be -074
to + 074.
Figure 7.11.: TCU main board (zoom II).
94 QCL user’s manual v3.1.3
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