Hi,

I wish to use the relay outputs A and B to power an external device when a certain condition is met. To test the functioning of the relay, I tried activating the relay by sending a simple 1RELAY=1 command and measuring the resistance between terminals A and B, thinking that the resistance should be close to zero when the relay is activated.

However, this was not the case (the multimeter read OL), indicating that the relay may not be activated. What am I missing?

Thanks and regards,
Sameet

Looks strange, do you hear the relay "clicking" switching it using the commands 1RELAY=1 and 1RELAY=0? Other than this check I have no other idea, maybe it's an hardware fault. As an alternative you may use an external relay connected to digital output as indicated in figure 103 page 231 of DT80 user manual.

Let us know, bye

Hi teo,

Thanks for your reply. Sending the 1RELAY=1 and 1RELAY=0 commands as you suggested did activate the relay, so the relay is functioning.

I feel I have to elaborate on/change my original post; 1RELAY=1 command I sent was as the action of an alarm; the code is as below:

ALARMR1(4F(=3CV,"Beam 3 (6 Modules)",E)<6.0000){[1RELAY=1]}

The sensor is a flow meter and DT80 is measuring the output frequency. Whenever the alarm was triggered (the bell on the DeLogger display went from grey to yellow), the relay contacts would still be open.

If I changed the 1RELAY=1 alarm action to SATN, the Attention LED would light up whenever the alarm condition was triggered. I tried the same thing today on a different sensor channel, a Pt100 with the DT80 measuring resistance and the code is as below:

ALARMR5(103PT385(3W,=2CV,"Radiator Inlet",100)>40.0000){[1RELAY=1]}

In this case, when the alarm was triggered (the bell on the DeLogger display went from grey to yellow), the relay contacts did close. The two differences between the two measurements that I can see are that one (the flowmeter) uses an external excitation, the other (PT100) does not.

Secondly the PT100 is located on the CEM20 expansion module, whereas the flowmeter is located on the DT80 itself - would either of these (the external excitation, in my opinion) somehow limit the relay from activating?

I tried setting a CV to the flowmeter output and then setting the alarm condition based on the CV, but the program wouldn't work. My apology for misrepresenting the situation in my first post; please let me know how to tackle the problem.

Thanks and regards,
Sameet.

Good morning Sameet,

Relay operation is independent of the channel option. I have tested both of your alarm statements and they both work the relay as expected. I copied and pasted the code to DeTransfer and used a multi meter to check the resistance of the contacts on the relay.

Just check you don't have another alarm statement that turns the alarm off again. Also check you firmware version and upgrade to the latest, just in case there has been a firmware change I can't remember one to do with the relay but it won't hurt.

Cheers,
Roger

Hi Roger,

Thanks for your reply, I was able to get the alarm condition to work. With the turbine flowmeters that I have, when the flow goes to zero, the recorded frequency is -99999.999 "out of range".

This was preventing the alarm condition ALARMR1(102F("Experimental Modules",=6CV,E)<6.0000)1RELAY from being met and thus not activating the relay. I used a CV to convert this "out of range" condition to zero by using

6CV("Experimental Modules~lpm",ND,=11CV)=6CV*60/3500*(6CV>=0)
ALARMR4(11CV("Experimental Modules~lpm")<0.1000)1RELAY

and thus was able to set the alarm and activate the relay.
Thanks also to teo for his/her help. This topic can now be closed.

Regards,
Sameet.

Good afternoon sameet,

You won't be able to measure flow rates below the time out threshold. Have you considered using the high speed counters for your flow sensor?

If you use a high speed counter with the reset (R) and the Reading/ time difference (RS) it will return frequency.

Cheers,
Roger

Hi Roger,

My high speed counter channels are currently connected to two phase encoders. I have no other way of measuring the phase encoder output, so I cannot move the flowmeters to the 1...4C channels. Thanks for the suggestion though, I will try it out just to see how it works.

Regards,
Sameet.