User manual for - TEMPERATURE TRANSDUCER TRS-02a
An example of the transducers application is multipoint monitoring system (Figure 4.5).
Control panel (i.e. SPA-99 made by SIMEX) is used as MASTER in MODBUS network,
simultaneously it displays readed informations of all measurement points.
RS-485 bus should be equipped with termination resistors (100-150 ohm) on
both ends. The bus must not be ramified, and longer than 1 km.
Figure 4.5. Example application of the transducers
The PT-100 sensor can be connected to the device in typical 4-wire circuit (Figure 4.6 a),
3-wire circuit (Figure 4.6 b) or 2-wire circuit (Figure 4.6 c). Due to precision of measurement
4-wire circuit is recommended.
If 2 wire circuit is used, the resistance of wires should be as small as possible, to
avoid of measurement errors. Measured value can be corrected (constant
correction) writing 06h register (
measurement scale offset)
. Due to low precision 2-
wire connection is not recommended. Resistance of 0,3
Ω
causes with increasing of
results about 1°C. Simultaneously to increasing of wires resistance, increases
measurement error.
8
Measurement modules
Measurement modules
converter
RS-232
RS-485
RS-485
Control panel
PC host
