D8 Series User’s Guide
Chapter 2: Installation
34
White
Red
CH IN+
*CH IN-
Shield (if present)
Earth Ground
at Process End
Type J
thermocouple
Figure 2.14
– Termocouple Connections
CAUTION!
Ground loops and common mode noise can damage the controller or disrupt
measurements. To minimize ground loops and common mode noise:
• Do not mix grounded and ungrounded thermocouples. If any thermocouple connected
to the controller is of grounded construction, all thermocouples should be of grounded
construction and each should be connected to ground at the process end.
• Connect the earth ground terminal on TB2 to a good earth ground, but do not connect
the analog common to earth ground. The D8 uses a floating analog common for sensor
measurements. The noise protection circuits on the sensor inputs function correctly only if
the controller is correctly installed. See Ground Loops on page 27.
RTD Input Connections
RTD inputs require accessory resistors. Watlow recommends that you use a 100Ω, three-wire
platinum RTD to prevent reading errors due to cable resistance. If you use a two-wire RTD, jumper
the negative input to common. If you must use a four-wire RTD, leave the fourth wire unconnected.
100
Ω
RTD
IN +
IN -
Com
CH
CH
Figure 2.15
—RTD Connections
Voltage Input Connections
Voltage inputs with ranges greater than -10 to 60mV require accessory resistors. Special input
resistors installed at Watlow divide analog input voltages such that the controller sees a -10 to
60mV signal on the loop.
CH IN+
CH IN-
Device with
Output
Voltage
Figure 2.16
– Voltage Signal Connections
Содержание Controller Series D8
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