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1. The RTD signal is connected via a shielded cable. The cable should be routed away from power cables or other wires that
may cause electrical interference. The cables to be connected to the RTD are described as follows.
1) RTD sensors (type Pt100, Cu100, Cu50) can be connected using 2, 3 or 4-wire system, with 4-wire system connection
being the most accurate, 3-wire system the second most accurate and 2-wire system the worst. When the wire length is greater than
10m, it is recommended to use 4-wire connection to eliminate the wire resistance error.
2) In order to reduce the measurement error, and to avoid interference by noise, it is recommended to use a length of less
than 100m connection cable. The measurement error is caused by the impedance of the connection cable and may be inconsistent
for different channels in the same module, so it is necessary to adjust the characteristics of each channel, as described in 3
Characteristics setting. 2.
2. If there is excessive electrical interference, connect the shield ground terminal.
3. Connect the external power supply PE to a good earth.
4. The analogue power supply can be supplied from the 24 Vdc output of the main module or from another source that meets
the requirements.
5. Short the positive and negative terminals of the channel not in use to prevent false data being detected on this channel.
2 Instruction for use
2.1 Power indicator
Project
24Vdc (-10 % to +10 %) Maximum allowable ripple voltage 2 %
Analog circuits
50mA (from mains module or external power supply)
Digital Circuit
5Vdc, 70mA (from the main module)
2.2 Performance indicators
Project
RTD type: Pt100, Cu100, Cu50
Input signal
Number of channels: 4
Conversion speed
(15± 2%) ms × 4 channels (unused channels are not converted)
Rated temperature range
12-bit A/D conversion; temperature values stored in 16-bit binary complement
Digital output
Minimum resolution
Precision
± 0.5% of full scale
The analogue circuitry is isolated from the digital circuitry by an opto-coupler. The analogue circuitry is
Isolation
internally isolated from the module input 24Vdc supply. No isolation between analogue channels
2.3 Indicator light description
Project
Signal indicator
Expansion module rear stage interface
Expansion module front interface
3 Characteristic setting
(1) The input channel characteristics of the VC-4PT are a linear relationship between the channel analogue input temperature
A and the channel digital output D, which can be set by the user. Each channel can be interpreted as the model shown in Figure 3-
1. As it is linear, the channel characteristics can be determined by determining two points P0 (A0, D0) and P1 (A1, D1). Where
Table 2-1 Power supply indicators
Table 2-2 Performance indicators
Celsius (° C)
–150℃～+600℃
Pt100
–30℃～+120℃
Cu100
–30℃～+120℃
Cu50
–1500～+6000
Pt100
–300～+1200
Cu100
–300～+1200
Cu50
Pt100
0.2℃
Cu100
0.2℃
Cu50
0.2℃
RUN status indicator, blinking when normal
ERR error status indicator, illuminated on failure
Connection of rear modules, hot-swappable not supported
Connection of front-end modules, hot-swappable not supported
Indicator
Indicator
Pt100
Cu100
Cu50
Pt100
Cu100
Cu50
Pt100
Cu100
Cu50
Instruction
3
Fahrenheit (° F)
–238° F～+1112° F
–22° F～+248° F
–22° F～+248° F
–2380～+11120
–220～+2480
–220～+2480
0.36° F
0.36° F
0.36° F
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