LRF-3000H Handheld Ultrasonic Flowmeter
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5. Operating Instructions
5.1.
System Normal Identification
Press the
Menu
0
8
keys. If the letter “*R” displays on the screen, it indicates system normal.
If the letter “E” is displayed, it indicates that the current loop output is over ranged by 120%. This refers
to the settings in menu 57. Enter a larger value in menu 57, and the letter “E” will disappear. It can be
ignored if no current loop output is used.
If the letter “H” is displayed, it indicates that the ultrasonic signal detected is poor. For more information,
please refer to “Error Diagnosis”.
If the letter “G” is displayed, it indicates that system is adjusting the signal gain prior to the measurement.
Also, it means system normal. Only when the adjustment takes too long without stopping, can system be
identified as abnormal.
Letter “I” indicates no signal is being detected. Check to see if the transducer wiring connections are
correct, the transducers are securely installed, etc.
Letter “J” indicates a hardware defect exists. Normally, such a defect is temporary; it could be eliminated
by system reboot (power off and restart).
For further information, please refer to “Error Diagnosis”.
5.2.
Low Flow Cutoff Value
The data in M41is Low Flow Cutoff Value. If the flow rate falls below the low flow cutoff value, the flow
indification is driven to zero. This function can prevent the flow meter from reading flow after a pump as
shut down but there is still liquid movement in the pipe, which will result in totalization error. Generally,
0.01m/s is recommended to enter as the low flow cutoff point. The low flow cutoff value has no relation
to the measurement results once the velocity increase over the low flow cutoff value.
5.3.
Zero Setting
Once zero flow occurs, a zero point is established, i.e. as the measurement value reaches zero flow, it
indicates as zero. It is necessary to establish the true zero flow condition and program that set point into
the instrument.
If the zero set point is not at true zero flow, an offset will occur. For an ultrasonic Flowmeter, the
measurement difference from zero point cannot be ignored under low flow conditions. It is necessary to
perform a zero set calibration to improve low flow measurement accuracy.
Set Zero in Menu42, press
Enter
,wait for the processing indication at the bottom right corner of the screen
to reach“0”. Performing Set Zero with under flowing conditions may cause the flow to be displayed as “0”.
If so, it can be recovered via Menu 43.
5.4.
Scale Factor
Scale factor refers to the ratio between “actual value” and “reading value”. For example, when the
measurement is 2.00, and it is indicated as 1.98 on the instrument, the scale factor reading is 2/1.98. This
means that the best scale factor constant is 1.
However, it is difficult to keep the scale factor as “1” on the instrument especially in batch control
operations. The difference is called “consistency”.
The scale factor default is “1” for each instrument prior to shipment from the factory. The reason is that
the scale factors in the flowmeter are only limited by two parameters, i.e. the crystal oscillation frequency
and the transducer. It has no relation to any circuit parameters.
During operation, if there still exists possible difference in pipe parameters, etc., the “scale factor” may be
necessary to be changed when used on different pipes. Thus, scale factor calibration is specially designed
for calibrating the differences that result from application on different pipes. The scale factor entered
