Watlow QPAC - Manual (Page 23)

QPAC User's Guide 23 Chapter 3: How to Operate
Fixed Bias
Connector
Gain Pot
J3
TB-1
1
5
J1
08-5342
BV Fixed Bias Connector
& Gain Adjustment
cut resistor for volts input
Motherboard Connector
Current Limit Pot
(AL Card only)
Bias Pot Gain Pot
08-5411
TB-2
TB-1
4 to 20mA
5V
CT
1
2
1
5
AL Bias, Gain, & Current Limit
Adjustments
move jumper for mA
or volts dc input
Bias and Gain
Current Limit Adjustments
(AL Card only)
The AL Control Card is a phase angle control with the capability to limit the
maximum current to the load. A potentiometer on the AL adjusts the current
limit setting. See the AL (Rev. B) Control Card figure above. Use the follow-
ing steps to adjust the current limit on initial setup. The purpose of the proce-
dure is to bring the power to the load up slowly so that the maximum current
to the load is not exceeded before the current limit is adjusted.
Note: A short overcurrent through the load may occur, as the AL Card
circuitry detects the higher current, if the input signal from the temperature
control is abruptly increased.
1. Attach a clamp-on ammeter to the load line.
2. Adjust the AL card current limit potentiometer fully counterclockwise (for
minimum current flow).
3. Turn the temperature control on and adjust the input signal to the control
card for zero percent power.
4. Turn the power to the QPAC on.
5. Gradually increase the input signal.
6. Adjust the current limit potentiometer clockwise until current to the load
is measureable.
7. Gradually increase the input signal to 100% power, then adjust the cur-
rent limit potentiometer to obtain the desired maximum current to the
load.
NOTE:
The AL Current Limit
must be disabled (pot
fully clockwise - CW)
before bias and gain can
be adjusted.
AL (Rev. B) Control Card.
BV (Rev. B) Control Card.