Solartron Metrology Ametek OD2, Инструкция пользователя

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13
Part No. 501107 Issue 13
A 4-20mA Transmitter is suited to current-driven indicators and provides a directly compatible
interface with computerised data acquisition and control systems. The Transmitter (Figure 4.3)
draws 4mA to operate the electronics while the position of the transducer controls a 0-16mA
current sink wired in parallel. Thus, the position of the transducer is indicated by the current con-
sumption and a broken cable is identified by zero current. This inherent ability for fault indication,
together with its low susceptibility to electrical noise and cable resistance, and the need for only
two wires make the 4-20mA Transmitter ideal for use in industrial environments.
Fig. 4.3 - 4-20mA Transmitter Connections
A 0-20mA Transmitter (Figure 4.4) works on the same principle, but without linking the two current
drives. It can therefore be used with a simpler indicator although it needs a third wire.
Fig. 4.4 - 0-20mA Transmitter Connections
Supply
Transducer
Current Driven
Indicator
V
s
Resistance = R
Two Wire Transmitter
OD2 Transmitter
7
6
4
mA
5
0-16
mA
Supply
Transducer
Current Driven
Indicator
V
s
Three Wire Transmitter
OD2 Transmitter
Resistance = R
0-20
mA
7
6
4
mA
5