Arduino with AD7705 and pressure transducer

Other Hardware Sensors
1

I have a pressure transducer that outputs 0-5V. I also have an AD7705 I want to use the get the really high sample rate. The AD7705 sheet says it can handle unipolar analog input from 0-2.5V, so I'm guessing I need to make a voltage divider upstream of the AD7705. I also guess I don't need any gain. Do I just go from divider into AIN1+ and AIN1-? Do I need to use a reference voltage? Do I need to do anything special to get the max sampling rate?

Thanks!
Bill

2

Please post a link to the transducer. What is the response time?

3

It is an Ashcroft G2

The response time is 1ms

5

1ms

6

There is no point in sampling faster than 1000 Hz, which is trivial for the built in ADC of any Arduino. I did not see the response time mentioned in either of the linked documents, though.

7

The max is 500Hz but it is very accurate.

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8

I have another pdf on my computer which gives the response time as less than 1ms

9

So any advice on the circuit? Right now I only imagine a voltage divider > AD7705 > arduino > PC

10

My advice is to use the built-in Arduino ADC. You will need a voltage divider with a 3.3V Arduino.

11

So 500Hz is fast enough?

12

Yes

13

Interesting!

14

The AD7705 brings nothing to the project.

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15

This is an UNO R3. Do I still need the divider?

16

Have you considered ADS1115? 860Hz, I2C, 16(15bit) and in-built voltage reference. Many good libraries around.

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17

No. The Uno R3 built in ADC accepts 5V input, and since it more accurate than the pressure sensor, you gain nothing at all by using an external ADC.

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18

Can you show that math? The G2 performance is stated +/- 0.25%. You have 1023 counts for the Uno, 0-5V, where the +5V is the unstable USB voltage as reference. 5/1023.

19

The precision of the ADC on the Uno is 1/1024, or about 0.1% of full scale.

The accuracy is also 0.1% of full scale, provided that the ADC reference voltage is at least that accurately measured.

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21

So I am going straight from pressure transducer to A0, but only getting 260Hz. Any ideas?

Thx

22

Why do you think I'm only getting 260Hz from the arduino ADC? The code is just Serialprintln(analogRead(A0));. The baud rate is 115200.

Thx