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CLS200 Series User’s Guide
Chapter 2: Installation
34
NOTE!
When mixing current inputs with low-voltage inputs (thermocouples or voltage
inputs less than 1V) to a sixteen-loop controller, connect the current inputs to the IN+
and Ref Com terminals. If no low-voltage sensors are used, connect current inputs to the
IN+ and Com terminals on TB1. For all inputs to a four or eight-loop controller, connect
the sensors to the IN+ and IN- terminals.
CAUTION!
Ground loops and common mode noise can damage the controller or disrupt
measurements. To minimize ground loops and common mode noise:
• With a sixteen-loop controller, use only ungrounded thermocouples with each
thermocouple sheath electrically connected to earth ground. The negative sensor
terminals on sixteen-loop controllers are tied to analog common.
• With a four-loop or eight-loop controller, 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 CLS200 uses a floating analog common for sensor
measurements. The noise protection circuits on the sensor inputs function correctly only
when the controller is correctly installed. See
.
RTD Input Connections
This input type requires scaling resistors. Watlow recommends that you use a 100 W, 3-wire
platinum RTD to prevent reading errors due to cable resistance. If you use a 2-wire RTD, jumper the
negative input to common. If you must use a 4-wire RTD, leave the fourth wire unconnected.
100Ω RTD
CH IN +
Com
CH IN –
Figure 2.14
— RTD Connections
Reference Voltage Terminals
The +5V Ref and Ref Com terminals are provided in order to power external bridge circuits for
special sensors. Do not connect any other types of devices to these terminals.
Voltage Input Connections
This input type requires scaling resistors. Special input resistors installed at Watlow divide analog
input voltages such that the controller sees a -10 to 60mV signal on the loop.
Содержание CLS200
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