Dwyer UFB - Manual (Page 26)

3: Operating Procedures
22
3.3.3 Adjusting the calibration factor
With the system running:
1. Stop ( Stall) the totalizer facility and zero it (Paragraph 3.5).
2. Run the totalizer to measure the total flow over a 30-60 minute period, and note the total flow indicated by the
reference flow meter over the same period.
3. Calculate the % error between the UFB instrument and reference meters. If the error is greater than ±1%
calibrate the UFB as detailed below.
4. Press the Options key to access the FLOW
READING OPTION screen shown.
5. Scroll down and select Calibration factor
then press ENTER.
6. Change the calibration factor according to the
error calculated in step 3. For example, if the
instrument was reading 1% high then increase
the
Calibration factor value by 0.010.
Conversely, if the reading is 1% low then
decrease the calibration factor to 0.990.
7. Press ENTER to apply the change.
8. Select Roughness factor or Exit as
required and press ENTER.
Key Point: In order to cancel any applied offset, you must read the flow via Quick
Start. Any value that you trim-out using the offset adjustment will be added/
subtracted from the flow reading across the whole range.
Key Point: USE THIS FACILITY WITH CARE & ONLY WHERE NECESSARY
The instrument is fully calibrated before leaving the factory and under normal cir-
cumstances does not require further calibration when used on site.
This facility can be used to correct the flow indication where unavoidable errors occur
due to the lack of a straight pipe or where the sensors are forced to be fitted close to
the pipe-end, valve, junction etc.
Any adjustment must be made using a reference flowmeter fitted in the system.
FLOW READING OPTION * *
Data review
Zero Cutoff (m/s) : 0.010
Set zero flow (m/s) : 0.000
Damping (secs) : 10
Totalizer : Run
Reset +Total
Reset –Total
Calibration factor : 1.000
Roughness factor : 0.010
Alarm Settings :
Max Pulse Freq (Hz) : 10.00
Flow at Max Frequency : 200.00
Calculated Pulse Value: 2.00
Diagnostics
Select Totals : +Total
Exit