EDAC Electronics Ltd. EDAC700 RTU Technical Reference Manual page 11

3.5.3 Calibration Example 2
This Calibration procedure is longer and more involved but does produce a more
accurate calibration.
As discussed on the pervious page, four values are required, this is illustrated in the
table below.
Low Point
High Point
For this example we will use a pot which will display a 0-100% range. It could be a
Transducer in a reservoir measuring the percentage full level.
Displayed Engineering Units for the example will be percent.
The pot will have a physical output range of 0-10 volts.
1. Configure Analogue Input via the Program Mode.
2. Low V value = 0
3. High V value = 10
4. Low Eng units = 0
5. High Eng units = 100
6. Decimal place spk = 1
7. Input type = D Always Report (must be set to this to do calibration, can be
changed after calibration)
8. You need to record a suitable voice recording in both the "on Voice message" and
"off voice message". This message should be the same in both slots.
9. Go Back to Run Mode
10. Press down arrow twice to get to the Input display screen
11. Use left/right arrows to display your analogue input location
12. Set pot at lowest reading, for this example it will be 0 volts, display should read Zero
13. Using a calibrated DVM, measure the actual voltage at the input terminal and note it
down on paper
14. Set pot at highest reading, for this example it will be 10 volts, display should read
Ten, do not worry if it does not.
15. Using a calibrated DVM, measure the actual voltage at the input terminal and note it
down on paper.
16. Go back to Program Mode, and go back to configuring your analogue Input location
17. Enter the Low and High readings observed on the DVM into "Low V value" and "High
V value" , go back to Run Mode
18. Check readings on display at low and high end. Calculate the difference between
displayed reading and expected reading at each end. If the slope has been
calculated correctly, these calculated deference's should be very similar. This is the
offset.
19. Go back to Program Mode, and back to configuring your analogue Input location
20. Enter the calculated Offset into the appropriate Offset location.
21. Go back to Run Mode and check the displayed reading for low and high end.
22. Reading should know be calibrated.
23. You can continue to adjust the Offset and Multiplier to achieve better calibration
For greater flexibility with analogue inputs please refer to notes on Input Mapping.
Date: 31/10/12
Volts or mA's
Low mA or V
High mA or V
Page 11File: 700b Technical Manual ver1.9.3.docm
Engineering units
Low Eng Units
Hi Eng Units