Watlow CPC400 - Manual (Page 172)

Chapter 6: Troubleshooting and Reconfiguring CPC400 Series User’s Guide
158 Watlow Anafaze Doc. 0600-2900-2000
CAUTION! Scaling resistors are soldered to the circuit
board. Only qualified technicians should attempt
to install or remove these components. Improper
techniques, tools or materials can result in dam-
age to the controller that is not covered by the
warranty.
Input Circuit
The CPC400 can accept differential thermocouple, mVdc,
Vdc, mAdc and RTD inputs. Unless ordered with special in-
puts these controller accept only signals within the stan-
dard range -10 to +60 mV
Î (dc).
To accommodate other signals, the input circuit must be
modified. When configured for thermocouple inputs, 0
Ω re-
sistors are installed in all RC locations. To accommodate
voltage signals outside the standard range, milliamp cur-
rent signals or RTDs, resistors are added or replaced to
scale the signals to the standard range. These resistor can
be installed by Watlow Anafaze or by a qualified electronics
technician using scaling resistors supplied by Watlow
Anafaze.
Figure 6.6 shows the input circuit for one differential ana-
log input. See Current Inputs on page 159 through RTD In-
puts on page 161 for specific instructions and resistor
values for voltage, current and RTD inputs.
NOTE! When adding your own scaling resistors to the
controller, for voltage and RTD inputs you will
have to carefully remove one of the RC resistors
in order to install the resistor listed in the table.
Figure 6.6 Input Circuit
Com
IN-
RC (RTD)
IN+
RD
RP
Analog
Input
Terminal
Internal RP
+5 V Î (dc)
Reference
To CPC400
Circuitry
RC (Voltage)
+
-