USER MANUAL
TYPE ML-2012/13
Manufacturers of low power instruments
page 21
4.6.4 Bridge of Wheatstone
The bridge of Wheatstone (the principle of operation of a load cell) is a circuit, consisting of 4 resistors.
Below a circuit is given:
Given, all R’s are the same the output voltage will be 0 Volts. In practice, one of the resistors is replaced
by a variable resistor (often a strain gauge) . By varying the resistance of this resistor, the bridge will be
“unbalanced” and there will be an output Voltage, other than 0 Volts. To enable the circuit, the bridge has
to be powered by a very stable reverence Voltage, often called “Excitation Voltage”. The ML2013 has an
Excitation output for this purpose.
4.6.5 Excitation Output.
The ML-2013 has an Excitation output for powering load cells, or other devices. It is a single output with a
fixed precision voltage output. This Excitation output is driven by the Power Switch of the ML-2013.The
default, fixed, Excitation Voltage is 5.000 Volts. For most load cells, this is OK. However, if the user
wishes another value, it can be selected by selecting 3 soldering jumpers on the bottom side of the board.
Here is how to set the jumpers for the correct Excitation Voltage:
Excitation Voltage Configuration
SJ1
SJ2
SJ3
Voltage
Open
Closed
Open
2.500 V
Closed
Open
Open
5.000 V
Open
Closed
Open
7.500 V
The default excitation is 5.000 V
