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Capacitive Sensor addon

Capacitive Sensor addon

(OP)

I have a control arm, and there is some metal block wired in series with my capacitive sensor, and I am not sure what it is or what it does.

Anyone seen this before and can give me some intormaion?

RE: Capacitive Sensor addon

Haven't seen this and could use some more details about your application such as what you are measuring and how but a couple of options:

- Reference capacitor at ambient temp to control for temp at sensor
- Some sort of proximity switch

Are you sure it is in series?

RE: Capacitive Sensor addon

(OP)

It is definitely in series - no doubt there.

It may be a solenoid proximity switch, if so not like any I have ever seen.

The application is above an ink tank, the sensor(s) see a high/low level and fill the ink tank back up.

The valve opens up to fill the tank at 50mm from the sensor, and stops filling at 20mm from the sensor.

This makes me think it must be 2 sensor operating here, since a capacitive wouldn't get 50mm distance unless it was far bigger.

RE: Capacitive Sensor addon

Are there any openings or windows on the aluminum block?

Could it be an overflow cutoff switch in case of main sensor error? If this is the case it could be magnetic, thermal, ultrasonic, conductive, etc depending on the properties of your ink. You could test it by submerging it in ink and seeing if anything happens.

RE: Capacitive Sensor addon

(OP)

There are no openings or windows in the block.

This was sent to us by a client, who also does not know what it is, just that it no longer works. I don't have access to the factory, if I did this would be much much easier.

The parameters I was given is that it activates (fills the tank) at 50mm from the sensor(s), and de-activates (stops filling) at 20mm from the sensors.

The arm sits above the tanks.

My first thought was why not have one sensor inside the tank, but this does not work because it is used on different inks, colors, etc.

A capacitive sensor has only 2 states, on or off, so this other little block must be a sensor of some sort - just no idea what.
The capacitive would do the 20mm "top" end of the open tank, so this other sensor would do the lower end, 50mm sensing distance.

I don't think it would be magnetic or thermal. Ultrasonic is a possibility, the sensing distance works, but I don't see how such a closed box could be ultrasonic.


RE: Capacitive Sensor addon

I'd guess the yellow one is ultrasonic for that distance.

Alternatively, one is an infrared light source and the other is a receiver.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Capacitive Sensor addon

Setting aside the question of what it is, you can accomplish the job of both with a single ultrasonic sensor like one of these:http://www.instronics.com/Migatron_RPS401.html

Is it good enough to replicate the function or has your customer asked you to duplicate the setup?

RE: Capacitive Sensor addon

Looking at all the rest of that hardware are you sure the mystery sensor isn't a proximity sensor that detects metal as the arms maybe fold up? That would tell the system not to do something when folded??

Keith Cress
kcress - http://www.flaminsystems.com

RE: Capacitive Sensor addon

Good catch Keith!

RE: Capacitive Sensor addon

If wired in series could it be as simple as a reed switch as a permissve or interlock? Any sign of a magnet? How many cores in the cable connected to it?

RE: Capacitive Sensor addon

(OP)

There are 2 cores in the cable connected to it.

It is magnetic, but oddly only on the sides, not on the front end which I would have thought.

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