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P118i Ultrasonic Flowmeter and Analyzer
Reversion: 3.0.0 Page 21 of 49
4. Operating Instructions
4.1 System Normal Identification
Press the 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 "G" is displayed, it indicates that system is adjusting the signal gain prior to the measurement. Also, it
means system normal. Only in such a condition for a long time, can the instrument be proved to be 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.
For further information, please refer to "Error Diagnosis".
4.2 Low Flow Cutoff Value
The data in M41 is Low Flow Cutoff Value. If the flow rate falls below the low flow cutoff value, the flow
indication is deemed to be ZERO. This can prevent the flow meter accumulate the flow when the actual flow
is"0"after a pump was shut down. Generally, 0.03m/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 is higher than the low flow
cutoff value.
4.3 Zero Settings
When zero flow occurs an instrument may have a zero point which shows a measured value is not equal to
“
0
”
.This value indicates "Zero Offset". For any measuring instrument, the smaller the "Zero Offset" is, the better
the accuracy will be. If the zero set point is not at true zero flow, a measurement error will occur. The smaller the
measurement flow is, the larger the measurement error caused by the zero Offset will be. Only when zero point
reduced to an acceptable degree can the measuring error caused by the zero point can be ignored.
For an ultrasonic flowmeter, the measurement error caused by the zero point cannot be ignored under low flow
conditions. It is necessary to perform a static zero set calibration to improve the low flow measurement accuracy.
Set Zero in Menu42, press , and then wait for the processing indication or displayed Complete..If setting
Zero in flowing conditions, it may cause the flow to be displayed as "0". If so, it can be recovered via Menu 43.
4.4 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
productions. The difference is called "consistency".
During operation, there still exists possible difference in pipe parameters, etc. The "scale factor" may be necessary
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 must be one that results from actual flow
calibration. The scale factor can be input in Window M45.
4.5 4 ~ 20mA Current Loop Output
With a current loop output exceeding an accuracy of 0.1%, the flowmeter is programmable and configurable with
outputs such as 4 ~ 20mA selected in Menu 55. Please refer to Menu 55 in "Window Display Explanations" for
more information.
In Window M56, enter a 4mA flow value. Enter the 20mA flow value in Window M57. For example, if the flow
range in a specific pipe is 0 ~ 1000m
3
/h, enter 0 in Window M56 and 1000 in Window M57. If the flow ranges
from -1000~0~2000m3/h, configure the 20~4~20mA output by selecting in Window M55 when flow direction is
not an issue. Enter -1000 in Window M56 and 2000 in Window M57.