BS2 Project and ADC''s
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Okay, let me try a different approach. Sometimes I don't give enough info
and sometimes too much info.
I would like to read a sensor with a BS2, I know I will need an ADC, which
needs to be a 12 bit. Can anyone recommend an serial ADC with possibly a
4.096 built reference? I've used the 1298 before but I wanted something a
little more precise and since the 1298 uses the Vcc as it's reference I
wanted to avoid it (Unless someone has a great method to make it very
accurate and repeatable).
The next part does not pertain to a stamp, but does have something to do
with my project, if you can't help, at least try and point me in the right
direction.
The max my sensor puts out is 400mv, so I figured I would use an
instrumentation amp to increase this signal by approx. 10 x with a small
adjustment for calibration purposes. This would give me the full range of my
ADC and the best resolution, I think. The amp needs to be a single
voltage like + 5vdc and Grd. I was looking at the AD626 and I several
LTC1052's but I never used them before. Can someone tell me if I'm on the
right path or if they have another item which is easy to work with and is
fairly accurate?
I don't mind learning by hard knocks, but I rather not do it a dozen times
either.
Throw me a bone please....
Richard
Original Message
From: "Richard Skinner" <rwskinner@w...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, October 13, 2003 1:04 PM
Subject: [noparse][[/noparse]basicstamps] Sensor project
> I working on a small project which requires me to read a sensor which
> outputs from 0 mv to 400mv +/- 40 mv full scale. It's almost linear but
> does have a couple of items that could use some error correction. I have
> several questions regarding the electronics end and some on the math end.
> The sensor is an Oxygen sensor that reads from 0% to 25.5% o2. At 21% o2
it
> reads approx. 400mv.
>
> I don't know much about OP Amps but willing to learn. I figured I would
use
> an 8 bit ADC with a 4.096 reference, then use an OP Amp with a Gain of 10.
> I thought about using a pot to slightly adjust the gain in order to
> calibrate the sensor. The sensor always has zero output when it senses
zero
> input, so I was only going to adjust the high end. Would this be the
proper
> procedure?
>
> Next, the sensor exhibits a Temp Coefficient of 0.2% signal / Degree C so
I
> may want to perform a temp. correction for the temp at the sensor. The
temp
> would range from about Ambient (32F to 100F) to about 150 Degree F when
> operating in it's environment. It's calibrated in an Ambient condition.
I
> was leaning towards using an Thermistor to measure the temp during
> calibration, then correcting the displayed units for the operating temps.
>
> Any input would be greatly appreciated.
> Richard
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
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Body of the message will be ignored.
>
>
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>
>
and sometimes too much info.
I would like to read a sensor with a BS2, I know I will need an ADC, which
needs to be a 12 bit. Can anyone recommend an serial ADC with possibly a
4.096 built reference? I've used the 1298 before but I wanted something a
little more precise and since the 1298 uses the Vcc as it's reference I
wanted to avoid it (Unless someone has a great method to make it very
accurate and repeatable).
The next part does not pertain to a stamp, but does have something to do
with my project, if you can't help, at least try and point me in the right
direction.
The max my sensor puts out is 400mv, so I figured I would use an
instrumentation amp to increase this signal by approx. 10 x with a small
adjustment for calibration purposes. This would give me the full range of my
ADC and the best resolution, I think. The amp needs to be a single
voltage like + 5vdc and Grd. I was looking at the AD626 and I several
LTC1052's but I never used them before. Can someone tell me if I'm on the
right path or if they have another item which is easy to work with and is
fairly accurate?
I don't mind learning by hard knocks, but I rather not do it a dozen times
either.
Throw me a bone please....
Richard
Original Message
From: "Richard Skinner" <rwskinner@w...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, October 13, 2003 1:04 PM
Subject: [noparse][[/noparse]basicstamps] Sensor project
> I working on a small project which requires me to read a sensor which
> outputs from 0 mv to 400mv +/- 40 mv full scale. It's almost linear but
> does have a couple of items that could use some error correction. I have
> several questions regarding the electronics end and some on the math end.
> The sensor is an Oxygen sensor that reads from 0% to 25.5% o2. At 21% o2
it
> reads approx. 400mv.
>
> I don't know much about OP Amps but willing to learn. I figured I would
use
> an 8 bit ADC with a 4.096 reference, then use an OP Amp with a Gain of 10.
> I thought about using a pot to slightly adjust the gain in order to
> calibrate the sensor. The sensor always has zero output when it senses
zero
> input, so I was only going to adjust the high end. Would this be the
proper
> procedure?
>
> Next, the sensor exhibits a Temp Coefficient of 0.2% signal / Degree C so
I
> may want to perform a temp. correction for the temp at the sensor. The
temp
> would range from about Ambient (32F to 100F) to about 150 Degree F when
> operating in it's environment. It's calibrated in an Ambient condition.
I
> was leaning towards using an Thermistor to measure the temp during
> calibration, then correcting the displayed units for the operating temps.
>
> Any input would be greatly appreciated.
> Richard
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>