User`s guide

Chapter 7: Troubleshooting and Reconfiguring Series D8 User’s Guide
172 Watlow Anafaze Doc. 0600-3120-2000
Installing Scaling Resistors
Resistors are installed for all inputs on the D8. Inputs with sig-
nal ranges between -10 and +60 mV use 0
Ω resistors in the
RC position only. All other input signals require special input
scaling resistors.
CAUTION! Scaling resistors are soldered to the circuit
board. Only qualified technicians should at-
tempt to install or remove these components.
Improper techniques, tools or materials can
result in damage to the controller that is not
covered by the warranty.
Input Circuit
The D8 can accept thermocouple, mVdc, Vdc, mAdc and
RTD inputs. Unless ordered with special inputs these control-
ler accept only signals within the standard range -10 to 60
mVdc.
To accommodate other signals, the input circuit must be mod-
ified. When configured for thermocouple inputs, 0
Ω resistors
are installed in all RC locations. To accommodate voltage sig-
nals outside the standard range, milliamp current 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 7.4 shows the input circuit for one differential analog
input. See Current Inputs on page 173 through RTD Inputs on
page 175 for specific instructions and resistor values for volt-
age, 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.