Weidmüller Pty Ltd
ACT20P Bridge
Note: Subject to technical alterations without notice
QS610001101 • 08/2009
Q
UICKSTART
GUIDE
Operation
General
The ACT20P Bridge is a DIN rail mounted, signal conditioner for
industrial strain gauge bridges. It provides a precise excitation voltage
for the bridge, and converts the input measurement to an isolated
current/voltage signal.
Strain gauge bridges are used for various measurements like weight,
force, tension, pressure, torque, and deflection.
Bridge excitation supply
Voltage sense connections are provided so that the excitation voltage
can be measured at the bridge. Known as ‘remote sensing’ this
method compensates for cabling and contact resistance errors. It is
recommended for all new installations or where an upgrade is possible.
Remote sensing wiring requires three twisted pairs.
TARE adjustment
The installed strain gauge is normally subjected to an initial load
independent of the measurement taken. The TARE connection allows
you to correct for this initial loading by operating a switch.
Alternatively there is a button on the front of the unit (under the front
cover) that performs the same function. Press for two seconds to
correct for the initial load (the ‘CAL HI’ LED will light for one second).
Gauge factor
Every strain gauge has a ‘gauge factor’ which gives the output voltage
at full-scale for a one volt excitation voltage (given in mV/V). You
multiply this by the bridge excitation voltage to get the output voltage
when the gauge is fully loaded. For example, a load cell with 10V
excitation and 2mV/V gauge factor will give 20mV when fully loaded.
The meaning of a 20mV output depends on the type of the strain
gauge. If it was designed to measure 0-1000Kg then 20mV indicates a
1000Kg load.
Cleaning
The case can be wiped with a damp cloth. De-energise the unit before
cleaning.
Setup
General
The ACT20P Bridge has internal switch settings that determine
the excitation voltage (5V or 10V) and Input range limits. Select the
appropriate settings from the table below.
Once you have set the DIP switches, you simply calibrate the unit to
the input and output range for your application.
Front panel DIP Switch settings
Switch Action if On Action if Off
1 10V Excitation 5V Excitation
2 mA Output Voltage Output
3 10mV Span
Turn off for other ranges
4 20mV Span
5 30mV Span
6 50mV Span
7
4-wire Measurement 6-wire Measurement
8
Installation
Caution: These units must only be installed by qualified staff in
accordance with the information given in this manual and all relevant
national electrical wiring and safety rules must be followed.
Locate the instrument in an area that is free from dust, moisture and
corrosive gases. Do not cover the ventilation holes at the side of the
case.
Connections
For effective protection from electromagnetic noise, all signal cables
must be shielded, or located on conductive trays or in conduits.
Strip wires to 7mm from the ends. Use a suitable ferrule for multi-
stranded wires (do not solder).
Power Supply Requirements
Power Supply Ratings are as follows:
Voltage Range Nominal Voltage Power
10 – 60 Vdc 24 Vdc 3 W (at 24 V dc)
Environmental conditions
Relative humidity: 10-90% (non-condensing)
Ambient temperature: -40° to 70°C
[+ Sense]
[+ Excitation]
[− Excitation]
[− Sense]
[− Signal]
[+ Signal]
1321 22 1411 12
ACT20P Bridge
Input connections for ACT20P Bridge with
switches set for 6-Wire measurement
[+ Excitation]
[− Excitation]
[− Signal]
[+ Signal]
21 22 11 12
ACT20P Bridge
Input connections for ACT20P Bridge with
switches set for 4-Wire measurement
Connections
Terminal Signal
11
Signal −
Input signal
12
Signal +
13
Sense +
Bridge Excitation Voltage
14
Sense −
21
Excitation +
22
Excitation −
23
Tare +
External Tare switch
24
Tare −
41 mA Output −
Output signal
42 Output +
43 mA Test Point −
44
Voltage Output −
44 mA Test Point +
54 +
Power Supply
53 −
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