1135 voltage sensor

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cizzi
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1135 voltage sensor

Postby cizzi » Mon Nov 01, 2010 3:09 pm

i'm using a 1135 phidget voltage sensor, I'm using the Raw value for maximum accuracy using this formula

voltage=(((value / 4.095 / 200.) - 2.5)/0.0681);

yet the result is not accurate at all, i think on a 12.36v battery (tested using a good voltmeter), the phidget reports 12.73v, which is completely off, with the error % reported in the product specs why am I getting such a difference or is this normal???

cizzi
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Re: 1135 voltage sensor

Postby cizzi » Mon Nov 01, 2010 3:50 pm

cizzi wrote:i'm using a 1135 phidget voltage sensor, I'm using the Raw value for maximum accuracy using this formula

voltage=(((value / 4.095 / 200.) - 2.5)/0.0681);

yet the result is not accurate at all, i think on a 12.36v battery (tested using a good voltmeter), the phidget reports 12.73v, which is completely off, with the error % reported in the product specs why am I getting such a difference or is this normal???


i get these bogus values with both the phidget interface 8/8/8 and the arduino duemillenove

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Patrick
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Re: 1135 voltage sensor

Postby Patrick » Tue Nov 02, 2010 10:24 am

Do you have the 8/8/8 in non-ratiometric mode?

-Patrick

cizzi
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Re: 1135 voltage sensor

Postby cizzi » Tue Nov 02, 2010 11:37 am

patrick wrote:Do you have the 8/8/8 in non-ratiometric mode?

-Patrick


i don't know, how do I check the status of that, and how do I toggle it?

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Patrick
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Re: 1135 voltage sensor

Postby Patrick » Tue Nov 02, 2010 12:02 pm

Well, depends on your language, but:

Code: Select all

ifkit.Ratiometric = false;

The default is true, as most sensors are ratiometric, but 1135 is non-ratiometric.

-Patrick

cizzi
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Re: 1135 voltage sensor

Postby cizzi » Tue Nov 02, 2010 12:25 pm

patrick wrote:Well, depends on your language, but:

Code: Select all

ifkit.Ratiometric = false;

The default is true, as most sensors are ratiometric, but 1135 is non-ratiometric.

-Patrick


For my program I used

CPhidgetInterfaceKit_setRatiometric(ifKit, 0);

Which gave me the same result (I allready had it disabled in my code not knowing) and also tried setting it to 1.

I think the problem is just the accuracy of the device, I should have checked the specs in more detail before purchasing it for my application.

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Patrick
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Re: 1135 voltage sensor

Postby Patrick » Tue Nov 02, 2010 1:21 pm

Are you running your conversion in the sensor change handler? Maybe you could try setting the sensitivity to 1.

The manual states a worst case error of 2% and typical 0.7%. The case that you mention has an error of 3%, assuming that your voltmeter is accurate, so you should be able to get better accuracy - or our specs are wrong, or the sensor is bad.

Also, does the sensor output 500 at 0v? There may be a consistent offset error that you could easily correct for.

-Patrick

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Re: 1135 voltage sensor

Postby cizzi » Tue Nov 02, 2010 1:37 pm

patrick wrote:Are you running your conversion in the sensor change handler? Maybe you could try setting the sensitivity to 1.

The manual states a worst case error of 2% and typical 0.7%. The case that you mention has an error of 3%, assuming that your voltmeter is accurate, so you should be able to get better accuracy - or our specs are wrong, or the sensor is bad.

Also, does the sensor output 500 at 0v? There may be a consistent offset error that you could easily correct for.

-Patrick



I set the sensitivity to 1, I set the ratiometric to 0 and with 0V reference point I get values of 494 to 512.. still not precise, I just needed 2 decimal precision to monitor the state of charge of a deep cycle 12v battery

cizzi
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Re: 1135 voltage sensor

Postby cizzi » Tue Nov 02, 2010 2:03 pm

cizzi wrote:
patrick wrote:Are you running your conversion in the sensor change handler? Maybe you could try setting the sensitivity to 1.

The manual states a worst case error of 2% and typical 0.7%. The case that you mention has an error of 3%, assuming that your voltmeter is accurate, so you should be able to get better accuracy - or our specs are wrong, or the sensor is bad.

Also, does the sensor output 500 at 0v? There may be a consistent offset error that you could easily correct for.

-Patrick



I set the sensitivity to 1, I set the ratiometric to 0 and with 0V reference point I get values of 494 to 512.. still not precise, I just needed 2 decimal precision to monitor the state of charge of a deep cycle 12v battery


ok i managed to get it to -/+ 0.04V error margin which is acceptable.. by using the raw sensor value and adjusting it to the 0V reference point

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Re: 1135 voltage sensor

Postby Quadro » Thu Sep 01, 2011 7:52 am

Patrick wrote:Are you running your conversion in the sensor change handler? Maybe you could try setting the sensitivity to 1.

The manual states a worst case error of 2% and typical 0.7%. The case that you mention has an error of 3%, assuming that your voltmeter is accurate, so you should be able to get better accuracy - or our specs are wrong, or the sensor is bad.

Also, does the sensor output 500 at 0v? There may be a consistent offset error that you could easily correct for.

-Patrick


Hi!

I have the same problem as cizzi. I have 3 Precision Voltage Sensors (1135) and a SBC2 but every sensor shows a voltage of 6.755 V (result of the Phidget Control Panel) instead of 6.95 V (measured with different digital multimeters). This means an error of ~3%.

Ratiometric is set to 0 and sensitivity is set to 1. The output of every sensor at 0 V is ~500.

Any idea why the results are such inaccurate and how to improve them?


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