4-20ma.Sensor req18-24volt dc.
We can not find ac power supply.
Only power source is batt12v and solar panel.
Please advice how to do. Thanks
Hi
you can use a DC-DC converter (from12to24)
Like this for example
https://docs-emea.rs-online.com/webdocs/1621/0900766b81621ddc.pdf
It depends on the energy available and the measurement frequency, it may be necessary to switch on and off only when needed. With SW12.
Smile
Thank you for your advice. But we have another question:
- sensor is 4-20ma, 2-wire. using external power 24VDC via converter as your recommend.
Can we use CR1000X G & RG terminal? or need to buy CURS100?
- We intend to using with Multiplexer AM16/32 (old) that we not using it for measure low voltage anymore,
is it possible to use AM16/32?
Regard,
Chalit I
STS
Hi Chalit
The converter must have the negative in common between the input and the output, so it will be possible to use the two terminals RG could be a solution.
With the use of the multiplexer, set as 32x2, you could connect the COM H and COM L outputs to the two RG terminals on the logger.
In any case, in order to avoid a fast consumption of the contacts of the relay to switch the current of the sensor (besides turning it on and off brutally at each measurement) I would prefer to put a CURS100 or 100 OHM resistor stable in temperature (PPM) and precise, according to the application and the desired precision, on each sensor, then on each terminal H & L of the multiplexer (and to G).
Regards
Smile
Hi Smile
Please see sketch diagram for you review/comment.
https://drive.google.com/file/d/1rNQ9d20g7G30wL9D3u72paS7ZjuJWv5H/view?usp=sharing
Chalit I
Hi Chalit
I was thinking of a quite different connection, I hope my link to the circuit works. And anyway or use RG or use CSRS100, together no.
http://it.tinypic.com/r/2ijgspk/9
Smile
Hi Smile
Its work very well !!
However,
1) all sensor have to be power up by SW12-on , then take all reading after that SW12-off. (each sensor consume 7mA)
2) rather messy, complex to wiring.
Thank you
Chalit I
Hi
The great thing about CS systems is that it allows you to adapt to the specifications required by even complex systems, and also that the same thing can be done in different ways, within certain limits. I have been working there since 85.
http://it.tinypic.com/r/ezlppz/9
With this other circuit, which I don't like so much, the wiring I think is more streamlined, but it could take some capacities and a delay in reading, after each clock to send the single sensor that turns on (like a warmup).
would also be concerned about the current that passes each time on the relay contacts.
A lot depends on the measurement frequency, but I don't like to think of continuously switching on and off with relays the sensors, current spikes and many failures happen just in this phase.....
The MUX manual says:
Maximum Switching Current 500 mA
(Switching currents greater than 30 mA [occasional 50 mA current is acceptable] will degrade the contact surfaces of the mechanical relays and increase their resistance. This will adversely affect the suitability of these relays to multiplex it is no longer useful for switching voltage in excess of 30 mA.)
Smile
Hi Smile
Below is a code:
'---------------------------------------------------------
PortSet (C1,1) 'Reset Multiplexer
Delay(0,100,MSEC)
SW12(SW12_2,1,1)
Delay(0,6,Sec) 'WarmUp all 4-20mA sensor about 5 sec before take measurement
For k=1 To NumOf4_20mASensor
PulsePort (C2,10000) 'Clocking Multiplexer
Delay(0,1000,MSEC)
VoltDiff (S4_20mA(k),1,mV5000C,1,True ,2000,50,0.01,0)
Next
SW12(SW12_2,0,1)
PortSet (C1,0)
'---------------------------------------------------------
Can you advice me
1. I delay 1000msec of Multiplexer switching, it can go faster but i use 1000msec. Is this set- good for multiplexer life time or not.
2. logger is ready to deploy at site as link below
https://drive.google.com/file/d/1DyLy86ZkxSkyjn-Y8YRBz9vbYXMTIXay/view?usp=drivesdk
3. logger is plan to use for 13 months of tilt monitoring (8ch) of historical buidling. Reading ever 5 min and send data via modem. Power by solar cell 60W.
PS. this is the old multiplexer, mode 2x32 often skip ch1. But mode 4x16 is ok
and reading on ch5+ is very stable than ch1-4.
Thank you very much.
Chalit I
Hi
sorry for the delay, but I was out of office.
What scheme did you use for the electrical connections between loggers, mux and sensors?
how is it the scan rate?
My last scheme provides single ended measurements (not diff) for each sensor and the MUX set as 2x32, so at each clock, 2 single ended instructions are needed for the two sensors wired in that moment to the logger (by the mux). Your program is for a different scheme.
for example (my last scheme)
PortSet (C1,1) 'Reset Multiplexer
Delay(0,100,MSEC)
SW12(SW12_2,1,1)
Delay(0,6,Sec) 'WarmUp all 4-20mA sensor about 5 sec before take measurement
For k=1 To NumOf4_20mASensor step 2
PulsePort (C2,10000) 'Clocking Multiplexer
Delay(0,1000,MSEC)
Voltse (S4_20mA(k),1,mV5000C,1,True ,2000,50,0.01,0)
Voltse (S4_20mA(k+1),1,mV5000C,2,True ,2000,50,0.01,0)
or (if use RGchannels)
CurrentSE(S4_20mA(k),1,mV1000,RG1,True,0,50,0.01,0)
CurrentSE(S4_20mA(k+1),1,mV1000,RG2,True,0,50,0.01,0)
Next
SW12(SW12_2,0,1)
PortSet (C1,0)
Regards
Smile
This post is under review.