Zisterne Füllstand

[HartmutB]

Addition:

I'm not really sure, as my (somehow working) Rewalux sensor has only 2 wires as well. It is connected to my AE/S 4.2 as MatthiasS has explained on his web page (http://www.schmidt213.eu/fra/).

Maybe you can connect the probe in combination with a power supply identically, but I don't know.


Regards,
Hartmut

[Warichet]

There are two things: If you have only two wires on your probe, then you ordered a 2-wire type "A" probe. I don't know, where this one is used.

?!?
Well, yes, the Prignitz PT-LM is a 2 wire probe

Type "B" would have been a 3-wire probe, more easy (or even worse: the only one) to install. .

Rhââ!

The second point: You need a driving power supply for the probe. Your AE/A 2.1 dosen't supply driving power (the AE/S 4.2 does), so an extra 24V DC (or less, depending on the probe) is needed.

Well, Makki did the installation, same probe, but with a Gira A/D converter
I guess the Gira DOES supply the extra driving power ???
So, I've but my bet on the wrong horse with this AE/A thing . It's looking fine with a sealed box, but ....

Maybe you can get your probe replaced or another one can tell you how to attach it, but the power supply is needed anyway.

That would really, really be the last resort.
It took more then 3 months to get this material delivered to me. DHL managed to get the package lost (those guys could loose an elephant in a corridor ). And a "not so well known" procedure from Eibmarkt calls for an 8 week recovery delay in case of international investigation.

Thank you for taking the time to look at my problem.
I don't know how come, but I always manage to get the right information when it's too late. Also, there is a very small chance of getting another probe, as the length of the cable is specified when ordering, mine is 18m.

[Warichet]

Maybe you can connect the probe in combination with a power supply identically

Yes, I think so.
I'll simply put the power source serial with the probe, just taking care of the polarity.
Technically, this is not a problem.
But given the very hostile environnement, it makes the problem worse. A water pit is obviously outside, so no easy place to install/hide the equipment. That's why I happily selected the AE/A 2.1, because it's already in a sealed box. But if I have to install a power source next to it, it ruins all my plans.

[HartmutB]

Well, Makki did the installation, same probe, but with a Gira A/D converter
I guess the Gira DOES supply the extra driving power ???

That's at least good news! If Makki uses the 2-wire as well, then the only thing you need is 24V DC and Makki, who (to be secure) tells us how he attached the probe.

Any A/D converter that does supply (the usually) 24V DC has a build in power supply and needs an extra 230V AC. This might be a problem (you just wrote something similar), so your conventer seems to be made basicly for a different usage (e.g. PT100 without extra supply voltage or similar).

What about using yellow and white in the bus cable for the 24V DC and putting the power supply inhouse (or using an existing one) ?


Regards,
Hartmut

[Warichet]

Any A/D converter that does supply (the usually) 24V DC has a build in power supply and needs an extra 230V AC.

I realize this now, as a KNX device is not allowed to take more than 10mA from the bus, hence the extra power has to come from somewhere else.

so your conventer seems to be made basicly for a different usage (e.g. PT100 without extra supply voltage or similar).

Indeed, it has plenty of options about temp measuring.
For debugging, I configured it for PT100, and it started to output a value. So I knew it wasn't (totally) dead.

What about using yellow and white in the bus cable for the 24V DC

Yes, the obvious solution. I was thinking about it, now that you restored some hope

[makki]

Now, @warichet I think the first thing would be to determine what exactly you ordered. They offer the PT-LM in different versions, if it gives response in a resistor-config I fear we're not talking about the same..
I ordered mine as
- 4-20mA (current output, but I'm not the right one to explain what that means..)
- 0-4 mWs (Wassersäule), i.e. 0-4 meters of water above the sensor, it basically measures the pressure-diff between the tube going out within the cable and the probe on the bottom of your reservoir.
So mine is connected with 2 wires, + and - only. As said it's on a Gira analog input (cheaper from ebay), as I use the AE/s for PT100 but thats shouldn't make any difference as they're quite similar.
I wouldn't disagree with Hartumut in electrical details never-ever, but from whats I read from the datasheets, the AE/A2.1 is able to provide enough power to the PT-LM sensor also. But the difference is surely, the analog input I use are all externally powered with 230V and have an addtl. powersupply for 24VDC

Makki

[Warichet]

the first thing would be to determine what exactly you ordered.

I must admit I haven't been carefull enough , well, not knowing the problematic behind it ...
Here is what is written on the probe.

PT-LM-10.0-4..20mA
MB: 16 mWC

Looks similar to yours, it's clearly ordered/designed for 16m water height, although it will almost never reach more then 15m water.

My mistake is to have bypassed the external power supply problematic. Also, the fact that the AE/A needs an external power is really not obvious in the doc. Beginners like me get caught the first time, I hate it
Those data sheet are for the people already knowing what they are looking for

it basically measures the pressure-diff between the tube going out within the cable and the probe on the bottom of your reservoir.

Aaah ! nice ! I didn't notice the small pipe in the cable.
Maybe that's why the cable is so expensive as it is a specially manufactured cable.
But .... but ... this has some implications ! the "end of the cable" must be in free contact with the atmosphere, heck, no silicone, no water, no cable-clamp/tie-wrap tighten like mad ....

As said it's on a Gira analog input

Lesson learned.
I'll buy a Gira A/D (and carefully put the AE/A on the shelf, collecting dust) instead of using an external power source. Would you be so kind to provide me with the references, please ?

but from whats I read from the datasheets, the AE/A2.1 is able to provide enough power to the PT-LM sensor also.

Mmmmm, no, don't think so. It's exactly the core of the discussion. From which data do you come to that conclusion ?

But the difference is surely, the analog input I use are all externally powered with 230V and have an addtl. powersupply for 24VDC

Yes, indeed

Thank you for those details

[HartmutB]

@Makki:

Schreib doch bitte mal, welchen genauen Gira Analogeingang Du verwendest und wo/wie Du den Sensor angeschlossen hast. Ich möchte das nochmal nachvollziehen.

Danke und Gruß
Hartmut

[DJGockel]

Hi,
ich hab zwar keine Sonde von Prignitz sondern wie schon gepostet von Kobold.
Es ist aber auch ein 2-Wire Sensor mit 4-20mA,
als Analogeingang verwende ich den Gira 1021 00
Anschluß 1 der Sonde an +24VDC einer externen Versorgung,
Anschluß 2 der Sonde ist beim 1021 00 auf der Klemme K1 angeschlossen.
Zusätzlich dann noch den GND der externen 24VDC Versorgung beim 1021 00 auf GND auflegen.

Einen Schaltplan kann ich morgen noch nach reichen, wenn Ihr wollt.

[makki]

@Warichet: Now I think got what I missed so far But all you need is a 12-30VDC supply (you should have that already somewhere?)
As I'm not sure, maybe Hartmut can confirm how to exactly connect this (external 12-30VDC -> PTLM -> AE/A).

But if you really get another input, go for the AE/S4.2 as I can 100% confirm it works for this purpose with 2 wires (as I had the PT-LM on it for tests). The current Gira model 1021 00 also needs an external 24V supply AFAIR!

@Hartmut: Gira 0960 00 (ist aber ziemlich alt, gibts glaub ich nicht mehr), + der Sonde an Us(+24VDC@max, - an K4

Makki

[HartmutB]

@Makki und @DJGockel:
Danke für die Hinweise, decken sich mit meiner Beschaltung des Rewalux (ist halt die von Matthias und die funktioniert ja noch an mehr Orten).

@Warichet:
Raymond, we've got three identical "settings", so it should be no problem now, except for wiring specialties you might have. Keep your existing and sealed A/D converter, simply add supply voltage.
If you have an "undrosseled" output at you KNX power supply, just use it (ok, my personal opinion). If you have another 12 to 30V DC power supply installed indoor with about 50mA available load, use this.

Connect GND of the power supply via the (hopefully unused) white wire of the bus cable and with PIN 1 or 3 of the AE/A2.1.
Connect VCC of the power supply via the (hopefully unused) yellow cable with "+" of the probe in the AE/A 2.1 box
Connect "-" of the probe with input A (pin 2) or B (pin 4) of the AE/A 2.1

Be happy again ...


Regards,
Hartmut

[Warichet]

it should be no problem now, except for wiring specialties you might have.

Indeed.
So I simulated the water pit with a 4m Ø100 PVC pipe, vertical, bottom sealed and filled with water.

Connect GND of the power supply with PIN 1 of the AE/A2.1.
Connect VCC of the power supply with "+" of the probe in the AE/A 2.1 box
Connect "-" of the probe with input A (pin 2) of the AE/A 2.1

I've done a similar wiring (don't know why the first test didn't work, maybe a bad contact, anyway, as everything is serial, should't make a difference). Also, I inserted a multimeter, serial with the PS, to read the 20mA.
GND of the power supply to the "-" of the probe
"+" of the probe to "0V" of the AE/A
"A" of the AE/A to "+" of the PS
I've put marks on the cable, every meter, to check the cable length. The reading of the water level are absolutely not accurate, nor linear. Although I can understand that there is an offset, depending on where the sensor is (the hole in the middle I guess), but then, that offset should be constant

Read - Meas - Diff
3,44 4,04 0,60
2,64 3,03 0,39
1,76 2,03 0,27
0,88 1,02 0,14

Heck, what would it be at 14m ? ?

Be happy again ...

That will be the most difficult part of the exercise

[HartmutB]

GND of the power supply to the "-" of the probe
"+" of the probe to "0V" of the AE/A
"A" of the AE/A to "+" of the PS

Hmmm.
That's not excactly the way, I told you. I'd give it a try with the proposed cabeling.
At least, you get some values, now. In addition, what about your settings in the ETS? I guess, you adjusted the values for minimum, maximum etc. for calibration (screenshot of settings) ?

Regards,
Hartmut


BTW: Low water conditions aren't so often these autumn days, so you've got about 7 to 8 month for getting it to work .

[Warichet]

That's not excactly the way, I told you.

I know, I know, it's not very logical, but seems to work ... somehow

I'd give it a try with the proposed cabeling.

Yes, Sir !

At least, you get some values, now.

Heck, better than nothing
But ... about those values .... Mmmm, I realize now that I ordered a 16m device. So I guess it is somehow calibrated for 16m. But in ETS I specified 14m. This might be wrong and might be the cause of the drift in the measured values. I thought "16m will be the max, ever" but I guess I MUST specify 16 in ETS to be consistent with the probe.

I guess, you adjusted the values for minimum, maximum etc. for calibration (screenshot of settings) ?

Yes, I think they are OK, at least that's what I understood from Makki's explanation.

Low water conditions aren't so often these autumn days, so you've got about 7 to 8 month for getting it to work

Well, for the first time in 4 years, the pit has been empty from the end of august till begin october. Almost 2 month without a drop

[HartmutB]

But ... about those values .... Mmmm, I realize now that I ordered a 16m device. So I guess it is somehow calibrated for 16m. But in ETS I specified 14m. This might be wrong and might be the cause of the drift in the measured values. I thought "16m will be the max, ever" but I guess I MUST specify 16 in ETS to be consistent with the probe.

Caught in action !

Of cause, you must specify the ordered 16m in the converter. Then it is working perfectly: If you multiply all measured values with 16/14=1,14 you have almost exactly the wanted values. Change your ETS setting to "16" and then get happy (one more try).

For the empty pit: Move to Germany, then you won't have *this* problem .

Regards,
Hartmut