Analog Inputs - ABB SM2000 User Manual

5.4 Analog Inputs

5.4.1 Current and Voltage – Fig. 5.6
Warnings.
• When the 'Input type' is set to 'Voltage', inputs
must be connected through a 500kΩ voltage
divider (part no. GR2000/0375). Voltages up to
2V can be measured without a divider, using the
milliVolt range.
• To avoid damage to multi-channel instruments, high
common mode voltages up to 500V r.m.s. max.
must be present on all channels, or not at all.
• The maximum channel-to-channel voltage (between
any two channels) must not exceed 12.5V (100V
high spec. inputs) or permanent damage to the
instrument's input circuitry may occur. To prevent
such damage, link the negative terminals on all
inputs. For applications where the available isolation
is required, this link must not be fitted.
5.4.2 Thermocouple – Fig. 5.6
Use the correct compensating cable between the thermocouple
and the terminals – see Table 5.1.
Automatic cold junction compensation (ACJC) is incorporated
but an independent cold (reference) junction may be used.
5.4.3 Resistance Thermometer (RTD) – Fig. 5.6
On applications requiring long leads it is preferable to use a
3-lead resistance thermometer.
If 2-lead resistance thermometers are used, each input must be
calibrated to take account of the lead resistance.
5.4.4 Transmitter Power Supply – Fig. 5.7
Note. The power supply board provides a 24V supply
capable of driving two 2-wire transmitters. Two
additional 24V power supplies are provided on the
transmitter power supply module boards, each of
which is capable of driving two 2-wire transmitters.
+
–
10Ω Resistor supplied
Voltage divider
in accessory pack.
(GR2000/0375)
required for
voltage inputs
A – Voltage B – Current
White
+
Red
–
Red
3rd Lead
Each lead must be of equal
resistance and less than 10Ω
D – 3-lead RTD
F – Volt Free Digital Input
Warning. Under no circumstances must
the spare input terminal be linked to the negative.
Note. Refer also to Fig. 5.5 for terminal numbers.
Fig. 5.6 Analog Input Connections
2-wire Transmitter Power Supply
(24V d.c., 45mA max.)
Analog Input
–
+
+
Tx
–
10Ω Shunt
Fig 5.7 Transmitter Power Supply
5 INSTALLATION...
+
+
–
–
C – Thermocouple
White
+
Red
–
3rd Lead
Sleeved
Link
E – 2-lead RTD
(and resistance)
Logic state Logic state
inactive active
+
–
85