Schlumberger G4 gasmeter - opto sensor

I've been trying to get my Schlumberger G4 gasmeter from 1981 up-and-running with the gasprobe.
Fiddling about with it all weekend, and browsing the web in the mean time my (provisional) conclusion is that it has no pulse output. Can anybody confirm this?
With that (possibly) confirmed, it does have a reflective thingy on the least significant digit, so probably an optic sensor could work. Did anybody get that working and/or is there something off the shelf available for this? Thanks.

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gebhardm's picture

If the type sign does not tell anything about "volume per pulse" then most likely the meter does not contain a magnet or pulse option; easiest way to find out is using a compass to detect a magnet...
Option then may be an optical reader if there is a reflecting sticker on one of the digits (most likely the 9 or 6 of the 0.001-wheel) - Bart is working on that according to an earlier post and there are certain schematics in the web using a CNY70 reflective optical sensor that will require some amplification of the reflection...

Harjo's picture

It doesn't say anything and the compass test revealed no magnets so it most likely does not have one.

I was browsing around Farnell for the CNY70 when I also found this device: OSRAM - SFH7740 (farnell number 1827024). Even though it is tiny I think it can do the trick: it already has a schmitt trigger onboard, detection distance seems to be right and it can run of 3.3V. The only (possible) issue I see is that is does not do a continuous measurement, but pulses every 90 ms. This makes the average current consumption very low, and it's probably not an issue for speed either (if your gas meter dials go around faster than 90ms/cycle, something is very wrong.....), but maybe there is a chance it will act funny if the reflective bit stops just halfway the detector (but the schmitt trigger should take care of that).
Anyway I've ordered one and keep you posted on the results.

cimm's picture

I have the Schlumberger G6 ( with the same characteristics. It does not seem to have a magnet so the gas probe doesn't work. It does have a reflective sticker on the least significant digit. Hope this might help someone. Waiting for Bart for the optical sensor.

automatronic's picture

He he he ... maximum pressure on Bart ! ;-)

icarus75's picture

Nah, not really. See this related forum thread. Putting a lock on this one.