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Alarm signal output of ultrasonic flow meters

 

Ultrasonic flow meters have two types of hardware alarms that are available with this instrument. One is the audible alarm, and the other is the ON/OFF output signal which can drive an alarm. The audible alarm is also called Buzzer. It is generated internally and can be configured in M77. The ON/OFF output signal is generated through the OCT or relay output which is connected to an external alarm circuitry.

The triggering sources of the alarming events for both the Buzzer and the ON/OFF alarm signal could be:

1)      There is no receiving signal

2)      The signal received is too weak

3)      The flow meter is not in normal measurement mode

4)      The flow direction is changed

5)      Overflow occurs at the analogue outputs by 120% or more

6)      Over flow occurs at the frequency output by 120% or more

7)      The flow rate is out of the specified range, which is configured in windows M73 and M74 for Alarm #1, and in windows M75 and M76 for alarm #2.

 

Example A: assume we need the Buzzer to start beeping when the flow meter is not ready in normal measurement. Switch to M77, select item ‘2.Abnormal Measurement State’

 

Example B: assume we need the Buzzer to start beeping when the flow rate is less than 300m3/h and greater than 2000m3/h. The following setup steps would be recommended:

1)      Enter flow rate lower limit 300 in M73 for #1 alarm,

2)      Enter flow rate upper limit 2000 in M74 for #1 alarm,

3)      Select item ’6.Alarm #1’ in M79

 

Example C: assume we need the OCT output to activate when flow rate exceeds 100~500m3/h and the relay output to activate when flow rate exceeds 600~1000m3/h. The following setup steps would be recommended:

1)      Enter flow rate lower limit 100 in M73

2)      Enter flow rate upper limit 500 in M74

3)      Enter flow rate lower limit 600 in M75

4)      Enter flow rate upper limit 1000 in M76

5)      Select item ’6.Alarm #1’ in M78

6)      Select item ’6.Alarm #1’ in M79