Hi,

Hope you can help, sure this must be quite straightforward but this is our first DT80 and I spent all day yesterday going round in circles! We have managed to program the unit in dEX to record and log pressures from 4 submersible transducers and two temperature sensors on the analog inputs.

There are two flow meters recording extracted and returned water to the geothermal bores which generate a 4-20mA signal that is sent to the PLC and to the BMS.

The PLC generates a 0-10 V output which is sent to a second PLC that closes a relay every time the flow meters record 1m3. Extract flow meter pulse relay has been connected to digital 1 and return to digital 2.

Seems complicated to me but it is not our system. We are trying to record the number of pulses every 15 minutes for each meter and once every 24 hours, with the counter resetting after each time period.

I have tried to enter various manual inputs but must be getting the language wrong - I'm sure it will be easier with time and experience but could really use a head start if someone could help.Thanks

Sorry just realized this should have been posted in newbies

bsa

Good morning bsa,

It is a very complex system. Why not read the flow 4-20 mA signal as scale to m^3 in the logger? Then you can remove a PLC. Oh well not your design.

DT80 can read a contact closure on digital inputs 1 to 4 (marked as 1D to 4D on DT80 terminal strip) and on the high speed counters (marked as 1C to 4C on DT80 terminal strip).

The digital will show on/ off and can act as slow speed counters (up 25 Hz) as well. But you need to connect one side of the contact closure do the digital input and the other to the digital ground on DT80 (please refer to wiring diagram DI1 on page 626 of DT80 user manual UM-85-B3).

In dEX select Add measurement and select Pulse counter. The counters (up to 25 Hz) are the digital inputs and the counters (up to 10 kHz) are the high speed counters.

Give your channels a name and select the wiring you are using. The channel can be reset after reading by checking the Reset counter " After the measurement is taken"

The simplest way to have a counter for 15 minutes and 24 hours is to link two digital inputs and read one with the schedule rate set to 15 minutes and the other digital read every 1 day.

Cheers,
Roger

Hello Roger,

Thanks for the reply. I agree, it does seem very complicated but I believe there are restrictions on the amount of water that can be pumped in any period, pumps cannot operate when the wells are at certain levels and the system has to be turned off if the temperature is greater than a 10 degree difference between extracted and recharged boreholes. Still - not my part of the works - all I have to do is log it.

We have got the wiring connected to the digital input and the other side to ground so I shall try adding a pulse counter again and using the reset as you suggest.

Do you know of a way to open up the dEX terminal without being connected to the logger to enable me to program in the office before returning to site?

This is the program we had loaded, is there anything obvious that we have missed? If this should work I will need to contact the PLC people to modify the pulsed output or would we be better off trying to get a 4-20mA mirror signal to DT80?

RS1S
RA"DAY_TMR"("b:",ALARMS:OV:100KB:W60,DATA:OV:1MB)1D
LOGONA
1HSC("EXTRACT FLOW",LM,R)
2HSC("RETURN FLOW",LM,R)
RB"15MIN_TMR"("b:",ALARMS:OV:100KB:W60,DATA:OV:1MB)15M
LOGONB
2HSC("RETURN FLOW2",LM,R)
RC"30MIN_TMR"("b:",ALARMS:OV:100KB:W60,DATA:OV:1MB)1M
LOGONC
1*L(N,"BH 1 LEVEL~METERS",LM,S1,NA,100)
1L(N,"BH 2 LEVEL~METERS",LM,S1,NA,100)
2L(N,"BH 3 LEVEL~METERS",LM,S1,NA,100)
2*L(N,"BH 4 LEVEL~METERS",LM,S1,NA,100)
3*L(N,"EXTRACT TEMP~DEGREE C",LM,S3,NA,100)
3L(N,"RETURN TEMP~DEGREE C",LM,S2,NA,100)

Cheers,
Bryn

Hi Bryn,

I like keeping things simple, there are a couple of approaches:

1. Use 4-20mA and read then in series.
   You will have to be very careful with your calibrations so the numbers on both systems tally. This will be simple to implement and doesn't need changes to PLC etc.

2. Read the pulses from the PLC. It is simple and will work well.

3. Read PLC Modbus registers.
   DT80 can be used as a Modbus master and can read the registers directly from the PLC.

Cheers,
Roger