Watlow CPC400 - Manual (Page 164)

Chapter 6: Troubleshooting and Reconfiguring CPC400 Series User’s Guide
150 Watlow Anafaze Doc. 0600-2900-2000
• For an RTD or process input, check that the correct in-
put scaling resistors are installed (see Installing Scal-
ing Resistors on page 157) and check the input scaling
parameter settings (see Setting Up a Process or Pulse
Input on page 58).
• If readings are erratic, look for sources of electrical
noise. See Noise Suppression on page 21.
• Contact your supplier for further troubleshooting
guidance.
Checking Control Outputs
To check control outputs:
• Set the loop you want to check to manual mode; see
Changing the Control Mode and Output Power on page
55.
• Set the output power percentage to the desired level;
see Changing the Control Mode and Output Power on
page 55
• Set the output type to on/off or TP; see Heat/Cool
Output Type on page 116.
If the control output is not connected to an output device
like a solid-state relay, connect an LED in series with a 1
k
Ω resistor from +5V to the output. (Connect the anode of
the LED to +5V.) The LED should be off when the output is
0 percent and on when the output is 100 percent.
Testing Control Output Devices
Connect the solid-state relay control terminals to the
CPC400 control output and connect a light bulb (or other
load that can easily be verified) to the output terminals on
the solid-state relay. Put the loop in manual mode and set
the output to 100 percent. The ac load should turn on.
Do not attempt to measure ac voltage at the output termi-
nals of the solid-state relay. Without a load connected, the
solid-state relay output terminals do not turn off. This
makes it difficult to determine whether the solid-state re-
lay is actually working. Measure the voltage across a load
or use a load that can be visually verified, such as a light
bulb.
Testing the TB18 and TB50
1. Turn on power to the controller.
2. Measure the +5V Î (dc) supply at the TB18 or TB50.
The voltage should be +4.75 to +5.25V Î (dc):
a) Connect the voltmeter’s common lead to TB18 ter-
minal 2 or TB50 terminal 3.