Hardy HI LPRE05 Shear Beams - Manual (Page 32)

HI HLPS SERIES LOAD POINT ASSEMBLY
Page 26
and measure the LPS output under “no
load” conditions. The reading should be
less than 1% of the full scale output.
NOTE: Sensors can shift up to about 10% of their full scale
and still function correctly.
Step 2. If the output has shifted more than 1%,
replace the sensor.
Assumption: A 5VDC excitation on a sensor with a
3mV/V output sensitivity, a 1% shift in zero balance
will yield a 0.1 mV/V change from the specification.
Bridge
Resistance Test Problem: Changes in Bridge Resistance
Cause: Failure of a compensating element, or by a
broken or burned bridge wire. Often cause by an elec-
trical transient such as lightning.
Remedy:
Step 1. Use an Ohmmeter and measure the resis-
tance between the EXC + and EXC- leads.
The value for the EXC leads should be
1106 ohms + - 5 ohms.
Step 2. Use an Ohmmeter and measure the resis-
tance between the SIG + and SIG - leads
The value for the SIG leads should be
1,000 ohms + - 1 ohm.
Step 3. Readings that exceed the ranges indicated
suggest damage and the load cell should
be throroughly inspected or replaced.
Resistance to
Ground Test Problem: Electrical leakage is creating an unstable
output from the instrument.
Cause: Water contamination in the load sensors or
cables.
Remedy:
Step 1. Tie together the load sensor excitation (2),
signal (2) and ground (1) wires.
NOTE: Be careful NOT to include the two C2 wires.