I have a paddlewheel flow meter that looks to be a solid block of plastic (polyoxymethylene) with no access to the electronics and no apparent seams. The power supply is 3.8-24 VDC, 50mA max. The output signal is a 0-120 Hz wave pulse train with a signal amplitude equal to the supply voltage. It has a type of connector in which the DC power and signal pass through the wall of the housing without any conductor contact. The clamp holds the connector in a specific orientation. The connector is 1/8" wide. See photos.

This flow meter was a custom build by Malema Engineering Corp.

It does work. Although I am unable test the pulse train, the signal is 12 VDC corresponding with my 12 VDC power supply and the voltage does fluctuate when I spin the paddlewheel by blowing through the meter.

Does anyone know what type a connector this is? I can't find anything like it.

Also, has anyone seen this type of design with the electronics contained in a plastic block?

 

That's not a connector, it's a Hell Effect transistor. Try putting a strong(ssh) magnet over the place where it mounts and rotate the wheel.

Don't go nuts with the magnet, you don't want to diminish the internal one.

 

Thanks Yaakov. Now it all makes sense. Quite the simple flow meter. As you can tell, I'm not a EE. Is there a simple way to convert the pulse train signal to a 4-20 mA signal?

 

I'd be looking for something like this: https://www.acromag.com/shop/signal...y-pulse-pwm-input-12-32v-dc-loop-local-power/

Just an example. You need to know the pulse frequency range. I would contact a sales engineer at a company that makes a converter and get help. Also, confirm my assertion that is a hall effect device. It seems obvious, but contact Malema and inquire about it. Their website seems very active and I expect they can help.

 

Thanks Yaakov. Now it all makes sense. Quite the simple flow meter. As you can tell, I'm not a EE. Is there a simple way to convert the pulse train signal to a 4-20 mA signal?

Define simple? Off-the-shelf units as @Yaakov identified are simple to set up, but expensive, typically $250-$350 or more. There are chips to do this conversion and a simple frequency to 20mA loop transmitter could be built by someone with reasonable soldering skills for a lot less than $100.