Rice Lake Simulators - Manual (Page 12)

8 Ranger Simulator Operation Guide
4.0 Troubleshooting With a Simulator
The most common use for load cell simulators is diagnosing problems with electronic scale indicators or with a
strain gauge load cell scale installation. Many problems in measurement systems involve drift or other situations,
which are not repeatable. A simulator gives a fixed point from which all other system components can be judged to
be properly working. Below are some tips for using a Ranger Series simulator as a troubleshooting tool.
Is the indicator working correctly?
• Connect the simulator directly to the indicator and see if the indicator is operational.
• If the indicator’s display is drifting, or not what is expected, there may be a problem with the analog input
stage, the excitation supply, or the sense circuitry.
• Several simulators may be connected in parallel to effectively “load” down the excitation supply circuits to
check for correct operation with multiple load cells.
What is the number of display graduations with the simulator output set to different settings?
• By measuring the excitation voltage and multiplying by the setting on the simulator, the actual input signal to
the indicator can be accurately calculated.
• This may help determine whether or not there is sufficient gain and low signal sensitivity in the indicator for
operation with low output systems.
• The linearity of the indicator may also be checked this way.
• If after installation and calibration of a system, a simulator is substituted for the load cells and the value
displayed for the zero and one of the other calibrated settings (i.e., 1 mV/V) are recorded, later recalibration
or repair can be greatly simplified by direct comparison of the displayed value with the previously recorded
values.
Does the displayed value change or start drifting, after other equipment or load cells are connected?
• Problems with transient protection boards, junction boxes, auxiliary power supplies and load cell cables can
be tracked down step by step by starting at the indicator and moving the simulator(s) down the line to the
load cells.
• When testing a portion of the system, make sure all other un-tested parts of the system are not connected.
When using the vernier (Ranger 1 or 5), do setpoint outputs and the display change as expected?
• Problems with output boards, setpoint routines and batching equipment can easily be found by using the
variable vernier output of the Ranger 1 or 5 to simulate the effect of changing amounts of weight on the
system.
• In addition, inappropriate filtering settings that may not be apparent normally, may sometimes be identified
this way.
Are the load cells working properly?
• By substituting a simulator for each load cell in a system, drifting cells, unevenly loaded cells, or other cell
related problems can be identified.
• After installation of a simulator in place of a load cell, note the zero and span readings for the simulator in
that particular position (vernier turned off).
• If the zero and span readings are substantially different when the simulator is moved from cell to cell, and
these differences are not consistent with the design of the scale, suspect cells can be easily identified.