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Jazz R31 - AN0 and AN1 input impedance


Mr. Petkov

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Dear support engineers,

Please let me know what is the actual input impedance of AN0 and AN1.

The document "JZ10-11-R31_TECH-SPEC_ 06-06.pdf" claims it is 154 Ohm.

A measurement with a multimeter shows 95.5 Ohm.

The way to come at this point is, that we have a problem with a 4-20mA transmitter.

The transmitter needs to have exactly 250 Ohm load, but we have Jazz R31 analog input.

Please expain for me, ASAP.

Kind regards,

Petkov.

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Hi Martin,

In 4-20 mA signal, as low is the impedance, as better. Usually, when you need to disable 4-20 mA analog signal, you need to short circuit it (0 Ohm load).

In all specs I saw in my life, it's stated "max permitted load" of the sensor/transducer. Are you sure in your case it's "exactly 250 ohm"? This is very strange. Can you send the spec of this transducer to support@unitronics.com?

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Hi Martin,

In 4-20 mA signal, as low is the impedance, as better. Usually, when you need to disable 4-20 mA analog signal, you need to short circuit it (0 Ohm load).

In all specs I saw in my life, it's stated "max permitted load" of the sensor/transducer. Are you sure in your case it's "exactly 250 ohm"? This is very strange. Can you send the spec of this transducer to support@unitronics.com?

Its really exactly 250 Ohm, as the company that manufactured this transmitter had designed the output to work in differential mode. But we have Jazz R31 that does not have such analog input. This is how we faced the problem.

Now we have to add resistor value at the transmitter output so its total value (Radditional + Rjazz_an0/1) equals 250 Ohm, and wire this active output pin to the left pin, which is the feedback input pin of this transmitter.

It is an "advice" from the manufacturer of the transmitter.

As you asked, all i can provide is its wiring. You can see that the 2-10V is wired directly, and the current outputs are not.

At least, what is your answer to my question for the input load resistance of AN0 and AN1 ??

post-2575-010465500 1305573952_thumb.jpg

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Its really exactly 250 Ohm, as the company that manufactured this transmitter had designed the output to work in differential mode. But we have Jazz R31 that does not have such analog input. This is how we faced the problem.

Now we have to add resistor value at the transmitter output so its total value (Radditional + Rjazz_an0/1) equals 250 Ohm, and wire this active output pin to the left pin, which is the feedback input pin of this transmitter.

It is an "advice" from the manufacturer of the transmitter.

As you asked, all i can provide is its wiring. You can see that the 2-10V is wired directly, and the current outputs are not.

At least, what is your answer to my question for the input load resistance of AN0 and AN1 ??

Just found i made a very rude mistake. Sorry to bother you.

It is surely 154 Ohm, i measured wrong as i had another 250 Ohm in parallel to the Jazz R31 (AN0 and AN1).

Thank you for your support !

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