Download IJ Instruments Ltd. IJ-6 SOFTWARE

11.2
11.0
Voltage (V)
10.8
10.6
10.4
10.2
10.0
9.8
0
10
20
30
40
50
Currrent (mA)
Fig. 17: SSR output voltage and current
Fig. 18 shows an example of connecting the temperature controller to a “brick-type” solid-state relay. A reed
relay or optoisolator can also be connected instead, providing the current draw is kept below the maximum of
40mA.
Solid-state relay
Observe correct
polarity!
To/from
switched load
+
Fig. 18: Connections for external solid-state relay
8.2.3
THERMOCOUPLE GROUND REFERENCE
A suitable thermocouple ground reference must be chosen, depending on whether the thermocouple is
floating or grounded. The two rightmost terminals of the terminal block, marked “0V” and “-”, are used for this
purpose. “0V” is connected to the negative supply rail of the temperature controller and hence to the negative
supply of the USB port. “-” is connected directly to the negative terminal of the thermocouple connector.
Depending on how these terminals are connected, either a floating or grounded thermocouple can be used, as
described below.
If the thermocouple is
•
•
bare (e.g. welded-bead) and not attached to anything (e.g. placed in mid-air to measure air
temperature)
bare and attached to an object, but the object itself is floating (not grounded)
then the thermocouple is “floating” relative to ground and the connection shown in Fig. 19 should be used. A
shorting link is placed between “0V” and “-”, thus connecting the negative terminal of the thermocouple to 0V.
The maximum allowed floating voltage is +/- 3V relative to ground.
20