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Hi.
I am newbie in this field and I would like to get from you some insight on how to setup a device to measure resistance wireless
My specs are :
Dimensions of the resistance is 2cmx2cm. Resistance is 100k to 100M Ohms (1V operations)
I would like the module for transmitting the resistance as small as it can .
On the other side, the receiver, which the dimensions are less relevant.

If you can recommend on equipment it will be great.

Thanks.
Sagi
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Hi.
I am newbie in this field and I would like to get from you some insight on how to setup a device for measuring resistance wireless
My specs are :
Dimensions of the resistance is 2cmx2cm. Resistance is 100k to 100M Ohms (1V operations)
I would like the module for transmitting the resistance as small as it can.
On the other side, the receiver, which the dimensions are less relevant.

If you can recommend on equipment it will be great.

Thanks.
Sagi
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Gosport, UK
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Please don't cross-post.

http://arduino.cc/forum/index.php/topic,121179.msg911750.html
http://arduino.cc/forum/index.php/topic,121178.msg911750.html
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Sorry,
Don't know which forum is the relevant one.
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If you can recommend on equipment it will be great.
Equipment for what? Measuring resistance? The Arduino can't. It measures voltages.

Sending the data? How much data? How often? How far? In what kind of environment? With what acceptable failure rate? Do you need bi-directional communication? What is your budget?
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Equipment for what? Measuring resistance? The Arduino can't. It measures voltages.

Sending the data? How much data? How often? How far? In what kind of environment? With what acceptable failure rate? Do you need bi-directional communication? What is your budget?

Equipment for building the setup for measuring the resistance of the resistor - I bring the resistor. Regarding Arduino's meas., I found some papers regarding using another resistor and subtracting the voltages to calculate the resistance of my resistor.

Sending data from the resistor site to the arduino - I need 6.5 digits ,every 0.1seconds at least. ambient env., not familiar with failure rate. One direction communication. Budget is less problem BUT the transmitter package should be as small as it can.

Thanks.
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What sort of wireless are you using? If you don't know yet, what sort of range and data rate do you need, and how many of these things will there be?
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I need 6.5 digits
That means 6 and half characters? How can you have half a character?

If that means 6 characters before the decimal point and 5 after the decimal point, dream on. There is no way you are reading the accuracy of a resistor to 0.00001 ohms, no matter how you try. Perhaps you ought to observe the tolerance of the resistors you are trying measure.

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every 0.1seconds at least
Sending 15 characters that often is not a problem. Reading the value to send, as you mechanically move the resistor in place could be.

Quote
not familiar with failure rate.
Have you ever pointed the remote at a TV, pushed a button, and nothing happened. Push the same button again, and the TV comes on? That is a 50% failure rate. Sending data is not guaranteed to be sent or to be received without getting mangled. Sending and receiving are not the issues, generally. It is interference that happens between the units that is a problem. Some radios handle interference better than others. Some frequencies are more prone to interference than others.

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Budget is less problem BUT the transmitter package should be as small as it can.
But it is the sender that needs to measure the resistance, and send the data. That will require at least some external hardware.

You still haven't mentioned range. That is a critical factor. Across the desk is one thing. Across the room is another. Across town is in a league of its own.
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That means 6 and half characters? How can you have half a character?

If that means 6 characters before the decimal point and 5 after the decimal point, dream on. There is no way you are reading the accuracy of a resistor to 0.00001 ohms, no matter how you try. Perhaps you ought to observe the tolerance of the resistors you are trying measure.

Well if he is talking digits like digital multimeters rate them:

6.5 digits means a display capablity of from 0000000 to 4999999 with the decimal point set anywhere among those digits depending on the ranges and units the DMM has avalible, and leading zeros blanked of course. Upon reading a value higher then the maximum display 'count' possible, the autoranging function would switch to the next higher units range if possible or change to a 'overflow' indication.

A full 7 digit display would of course span 0000000 to 9999999

Lefty



« Last Edit: September 02, 2012, 09:42:15 am by retrolefty » Logged

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Hi.
Thanks for the responses .
I do need to read resistance in the range of 6.5 digits meaning 100.000 MOhms, what retrolefty wrote is correct. the half, is +- 0.5 from the last digit. DMMs are known in doing that kind of measurements.
Failure rate should be very good as I need constant measuring (R vs. time).
The range is very small, even 50cm or less will be enough.
I need to read only one sensor.
The receiver can be as sophisticated and as big as it should to stand in the above requirement, what most important is the size of the transmitter+sensor.

If you have more questions, please let me know.
Thanks.
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What sort of wireless are you using?
I am open for suggestions range is 50cm
I need to read resistance in the range of 100MOhms with digits as : 100.000 +-0.5 Ohms
The size of the transmitter should be as low as it can. I am using 1V to operate the resistor.
data rate should be reading every 0.1sec (if it can be less than that, it will be great)
Accuracy and failure rate are very important.
Budget for this project is less problem.
I need to read only one resistor but may buy 2 or more setups.

Thanks.
Sagi
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Reading 0 to 100 000 000 Ohms to the nearest 0.5 Ohms will require at least a 28-bit a/d converter.
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Is it a problem ?
Where it should be placed ? in the receiver or transmitter?
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I don't think you connected the grounds, Dave.
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OP.

Do NOT cross-post, it simply wastes time.

Topics merged, third duplicate post deleted.
« Last Edit: September 02, 2012, 10:49:29 am by AWOL » Logged

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What sort of wireless are you using?
I am open for suggestions range is 50cm
I need to read resistance in the range of 100MOhms with digits as : 100.000 +-0.5 Ohms
The size of the transmitter should be as low as it can. I am using 1V to operate the resistor.
data rate should be reading every 0.1sec (if it can be less than that, it will be great)
Accuracy and failure rate are very important.
Budget for this project is less problem.
I need to read only one resistor but may buy 2 or more setups.

Thanks.
Sagi

Well the wireless link is pretty much boring, just selecting from the many types and methods available, not a big deal if you do your research. I however am somewhat interested in how you are making the resistance measurement using a one volt source to measure up to 100 megohms. At such low current I don't see how you can get accurate data without the measurement being swamped by low level noise. Any details on your actual measurement method and circuitry? A typical resistance measurement is made by feeding a constant current source through the unknown resistance and measuring the resultant voltage drop across the unknown resistance. How is your measurement made?

Lefty
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