Watlow QPAC User Manual download pdf (Page 22)

22 QPAC User's Guide Chapter 3: How to Operate

1. Connect a volt meter across the load or dummy load of the QPAC. Con-

nect a volt meter across, or milliamp meter in series with, the input signal

from the temperature controller. NOTE: AL card should be calibrated with

a dummy load on the QPAC

2. Apply power to the system.

3. Set the output signal of the temperature controller to zero or its minimum

output. The QPAC input is factory calibrated for full off at 4.2mA. Adjust

the bias potentiometer slowly CCW (counterclockwise) until the QPAC

output just comes on. Then turn CW (clockwise) until the output is just full

off as observed on the output volt meter. See the following gures for the

location of the bias and gain potentiometer on the Control Cards.

NOTE: The QBV card does not include a bias adjustment. A bias and gain

adjustment card can be added to the QBV card in the eld. Order Watlow

part number 08-7210. Follow this calibration procedure when using the

bias and gain card.

4a. AF and BF: Adjust the output of the temperature controller to full on

(5Vdc, 20mA, etc.). Adjust the gain potentiometer CW until the QPAC out-

put is just full on. The QPAC is factory calibrated to be full on at 19.8mA.

4b. BV and AL: Adjust the output of the temperature controller to full on

(5Vdc, 20mA, etc.). Adjust the gain potentiometer CCW until the QPAC

output is just full on. The QPAC is factory calibrated to be full on at

19.8mA.

5. When adjusting the bias and gain of the current limiting (AL) control card,

ensure that the current limiting is turned off. With the output of the temper-

ature control full on, adjust the current limit potentiometer until the QPAC

output is full on.

6. Repeat steps 3 and 4 until the QPAC turns full on with a full on signal

from the temperature control, and full off with the minimum input signal

from the temperature control. Steps 3 and 4 may need to be repeated a

few times (an adjustment made on one of the potentiometers affects the

adjustment of the other potentiometer).

7. Remove power, disconnect the meters, and reconnect the controlled load

to the QPAC if required.

Bias and Gain

AF (Rev. H) Control Card.

BF (Rev. D) Control Card.

Gain

Pot

Bias

Pot

08-5288

TB-2

R39

R38

TB1

4 to 20mA

move jumper for mA or volts dc input

Gain

Pot

Bias

Pot

08-5289

R17

TB-2

TB1

cut resistor R3 for volts dc input

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Watlow QPAC User Manual Page 22

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