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ADC recommendations for a DC (5V-0V) converter in noisy conditions

Hi, I have an ADC application where I am reading the output of a voltage transd ucer. The transducer has a 1.36 to 0.7 V range, the conversion rate is in t he range of 1 uS and probably around 10 bits of resolution will suffice. My main concern is that that the transducer output is 6 feet from the propose d circuit board location. I will low pass the the input to the A/D with a f ilter, however it is an electrically noisy environment in which I have litt le experience with and I am concerned with the length of the cable. Are the re any tips/tricks anyone can give in order to make accurate measurements o ver that length of cable? Any other concerns I should be aware of?

Thanks very much.

Reply to
djt294
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Well, use coax cable, and maybe a differential amp as a receiver for the signal from the sensor cable. You have 660 mV of signal, so this shouldn't be a really tough case. Possibly putting a ferrite core over the cable can help.

Another way is to make the signal fully differential at the sending end, and use twisted pair shielded cable (as in digital audio cable) and a differential amp as receiver.

Jon

Reply to
Jon Elson

djt294 wrote

Put the ADC next to the tranducer, and go digital on the wires. IIRC there are I2C ADCs (PCF8591 was an 8 channel 8 bit but who knows) else put a PIC (with 10bit ADC) next to the transducer and use its I2C out. Many PICs have a selectable internal reference voltage.

Reply to
<698839253X6D445TD

What acquisition bandwidth do you need? That limits how hard you can lowpass.

Two hazards: ground loops, and capacitive loading making your transducer oscillate.

What is the transducer?

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

+1

There is a reason why so much of the electronics world is digital.

Rick C.

Reply to
gnuarm.deletethisbit

Google for : voltage to current transducer

Once the signal is transmitted as current, it is easy to read on the receiving side.

Reply to
Sjouke Burry

Yep, this gets the problem good and dead. No drawback unless the cost of a dedicated ADC is much higher than the cost of good shielded wire and connectors. Heck, you might be able to use a USB probe; there's lots of sound (AC-coupled) digitizers that could get a minor modification. You can't beat that for cable cost and interface compatibility...

Reply to
whit3rd

nsducer. The transducer has a 1.36 to 0.7 V range, the conversion rate is i n the range of 1 uS and probably around 10 bits of resolution will suffice. My main concern is that that the transducer output is 6 feet from the prop osed circuit board location. I will low pass the the input to the A/D with a filter, however it is an electrically noisy environment in which I have l ittle experience with and I am concerned with the length of the cable. Are there any tips/tricks anyone can give in order to make accurate measurement s over that length of cable? Any other concerns I should be aware of?

Yeah. the more info you give the better the answer.

In general transducers on the ends of wires stink, (though you can make it work, wires with both braid and Al foil shield will help.) and it's sometimes better to think about adding some gain at the transducer. (gain can just be current, a unity gain buffer to drive the cable.)

George H.

Reply to
George Herold

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