Hi Again,

I have a flow meter which takes 5 volts and delivers a pulse on its output channel of 22000 pulses per litre, from 37to 917 Hz. I have powered the sensor +5 Vdc from SP, -5 Vdc from SR & GD The output is going into Digital Channel 8.

I have set parameter 47 to 5 volts. The program I am running is:

DT=\d 
BEGIN"TEST" 
CATTN 
'Spans and polynomial declarations 
'Thermistor declarations 
'Switches declarations 
'Parameter declarations 
P47=5 
'Global declarations 
RS1S 
'main schedule definitions 
1V 
'schedule definition 
RA1S LOGONA GA 
1V("Ultrasonic_Cm",.2) 
2V("Ultrasonic_Vcc") 
8C("Flow",1) 
END 
'end of program file

It seems very similar to the question asked at https://datatakerforum.com/index.php?u=/topic/610/flow-meters, however I have already turned on the power? Can you please advise what I am doing wrong to be getting an output of 8C - 0 Counts at all times, even when the oscilloscope is showing a good pulse on the output wire leading into digital channel 8?

Cheers
Ben

I don't think it will make a difference but just in case i should mention, I have put a 10 kOhms resistor between the 5 Vdc + and the output as suggested by the manufacturer:

"The output signal is a square wave signal, whose frequency varies linearly with flow rate. An external pull-up resistor (user-supplied) is required to insure that the open collector will sink less than 20 mA."

Interesting Development, I have found that channels 1 to 6 count correctly with my sensor. (Except channel 4 which seems to be dead).

Channels 7 to 16 seem to count but only one or sometimes two ticks each time I connect the sensor wire and not by the pulses on the sensor wire? I understand that there are some differences in the digital channels but I didn't expect the results I observed.

Regardless, I will use channels 1 to 6 (bar 4) to run my flow sensor.

Good morning Ben,

Digital inputs 1 to 8 have hardware that allows them to count frequencies up to about 10 kHz. Digital inputs 9 to 16 can count frequencies of up to 40 Hz. Please look at page 157 of the DT800 manual for further details.

Cheers,
Roger