Rice Lake Simulators - Manual (Page 8)

4 Ranger Simulator Operation Guide
2.1 Sample Calculations
A Ranger simulator may be used to perform calibration of scale systems prior to installation, or test installations
prior to installation. These are NOT procedures that can be used to certify a scale, but they will provide calibration
results satisfactory for most process weigh scales. Checking the scale calibration with known weights, or product
substitution (with a verified value) is recommended.
Using a simulator, digital voltmeter, and calculator to calibrate a scale
The following tools are required:
• Ranger simulator
• Digital voltmeter (4 digit minimum, 5 digit recommended)
• Calculator
Use the following steps to calibrate a scale using a simulator, digital voltmeter and calculator.
1. Millivolt Output Average Calculation:
If load cell calibration certificates are available for the system load cells, add the full scale millivolt output
values, and divide the sum by the number of load cells in the system.
Example: 2.997 + 3.002 + 2.995 + 2.999 = 11.993 / 4 = 2.99825 mV
If the load cell calibration certificates are not available, the nominal full scale millivolt output of the load
cells is used as the average millivolt output (2mV/V or 3mV/V most common).
Unless the system load cells vary significantly from the nominal value, the calibration results will be very
similar.
2. With your digital volt meter in the volts setting, measure the excitation voltage at the junction box home
run cable +/- excitation connections, and record the value.
3. Full Scale Output Signal Calculation:
Multiply the millivolt output average value from step 1, by the excitation voltage value from step 2.
Example: 2.99825 x 9.9875 = 29.945 mV.
This is the full scale millivolt output of the scale at the total load cell capacity (individual load cell capacity
x the number of load cells in the scale).
4. Total Load Cell Capacity:
Multiply the individual load cell capacity by the number of load cells in the system.
Example: (10,000 lb x 4 = 40,000 lb) 40,000 lb is the Total load cell capacity.
5. Signal per Scale Division:
Divide the total load cell capacity from step 4 by the scale resolution value (if the scale is to be calibrated
to 25,000 x 5 lb, the scale resolution value is 5 lb). 40,000 / 5 = 8,000. This is the number of divisions over
the total load cell capacity. Divide the full scale millivolt output value from step 3 by this value.
Example: (29.945 mV / 8,000 = 0.003743 mV) this is the signal per division (signal change for each
5 lb scale change, based on the example).
6. Span Range Signal Calculation:
Multiply the signal per division value from step 5 by the number of divisions over the calibrated range of
the scale (25,000 lb / 5 - 5000 x 0.003743 - 18.715625 mV). This is the span signal range to which the
scale will be calibrated.
7. With the scale empty, perform the normal ZERO calibration procedure (refer to the indicator manual).
Enter the calibrated scale capacity as the SPAN value (25,000 in the example in Step 6).
8. With your digital volt meter set to the millivolt range, measure the signal at the junction box home run
cable +/- signal connections, and record the value. this is the scale millivolt output value at calibrated
ZERO. Example: 4.245 mV (this is a random value selected for this exercise).
9. Span Calibration Signal Calculation: Add the calibrated ZERO millivolt value from Step 8 to the Span
Range value from Step 6 (18.715625 + 4.245 = 22.960). This is the Span Calibration Signal value.