Specifications - ACR Systems OWL 100 Manual

28 OWL Data Loggers
Maximum Impedance
An important consideration when choosing transducers is the requirement for loop impedance. This
simply refers to how much resistance the instrumentation (for example, the OWL logger) can have
before it will begin to cause problems. For current loop inputs, it is advantageous to have a very low
impedance (the OWL 20mA Current logger has a 100 ohm impedance). This helps to minimize the
voltage requirements and power consumption of the circuit. Check the specifications for the transmitter
to ensure the OWL's input impedance is acceptable.
Two-Wire Transmitters
Two-wire transmitters are transducers that form part of a current loop circuit. They vary the current flow
in accordance with changes in the variable with which they are sensing. Most two-wire transmitters
have a 4-20mA output. The connections are usually marked positive current loop (CL+) and negative
current loop (CL-). A transmitter can be found in a wiring diagram by looking for a single common path.
This type of transmitter is very popular and can be used with the OWL - see Figure 5-2.
Output
The specified output of a transmitter will determine whether it is compatible for use with the OWL
20mA Current logger. The most popular transmitter output is 4-20mA which can be used with the 0 to
24mA input on the OWL.
6.4

Specifications

Current Input
Ranges:
Max Voltage:
Accuracy:
Resolution:
Input Impedance:
Cable:
Equation:
Figure 5-2: Two Wire Transmitter Connection
0 to 24 mA
±7 VDC
±1% Full Scale
0.5% (8 bits)
100 W
2 m (6 ft) length with PVC jacket to IP67 connector
205
© 2001 ... ACR Sy stems Inc.