Help with the conversion math

[HenrikOlsson]

Yes, what pedja089 said. The only clue you provided is 54AL07H2210 which returns nothing on Google.

And, I have a feeling we've been thru this before..... The PIC ADC has a resolution of 10 bits, it returns values ranging from 0 to 1023.

/Henrik.

[Ramius]

Sorry guys. The PDF was too large (22 pages as it had all the devices in the series) so to upload so I had to make it smaller! Yes it is a 0.5 - 4.5v type ratiometric device. My A/D is showing a reading of 7040 at zero psi and when I do a divide by 16 I get 440 which I am assuming means .440 volts? With a voltmeter I see .541 volts so now I have not been able to make any sense of all of this. My best guess is that this would indicate a voltage range of .440 to 4.440? Where .440 is zero and 4.440 would be at .07psi? If the A/D were 10 bit and giving 1023 as a maximum value then a reading of 7040 could not be possible. I am just so totally lost and confused with so many numbers! I just completely do not understand! Thanks!

[richard]

Yes, what pedja089 said. The only clue you provided is 54AL07H2210 which returns nothing on Google.

And, I have a feeling we've been thru this before..... The PIC ADC has a resolution of 10 bits, it returns values ranging from 0 to 1023.

/Henrik.

its just like de ja vou again
http://www.picbasic.co.uk/forum/show...578#post128578

[HenrikOlsson]

Yeah, deja vu indeed....

Ed,
* The resolution of the ADC is 10 bits.
* It does not return a reading directly in Volts.
* Basically it takes the difference between Vref+ and VRef- and divides that by 1024 (2^10, the resolution of the ADC). Each "count" in the value is then "worth" that amount.

So, if VRef- is GND (0V) and VRef+ is 5V the difference between the two is 5V. Each "count" in the ADC result is then "worth" 5/1024=4.88mV.
If the ADC returns 745 the voltage at its input is 5/1024*745=3.638V

I can't make out anything from that datasheet, it's just garbage numbers when viewed on my machine. I managed to find this one. And, I'm guessing you've got the 7psi sensor, correct? If so then something like this might work. I have not tested it though so all bets are off....

Of course you need to configure pins etc as usual (!)

Accumulator VAR WORD
i VAR BYTE
ADResult VAR WORD

Accumulator = 0

Main:

For i = 0 to 39
  ADCIN 4, ADResult  
  Accumulator = Accumulator + ADResult
  PauseUs 500
NEXT

ADResult = Accumulator / 10   ' Psuedo 12bit resolution, ADResult is now 0-4092

' Sensor outputs 0.5V (ADResult=409 ) at 0psi (nominal)
' Sensor outputs 4.5V (ADResult=3683) at 7psi (nominal)

ADResult = ADResult - 409   ' Offset for zero output, ADResult is now 0 to 3274 for 0 to 7psi
ADResult = ADResult */ 547  ' Scale up, ADResult is now 0 to 6995 for 0 to 7psi 

' Display Pressure: x.xx psi
HSEROUT["Pressure: ", DEC ADResult/1000, ".", DEC2 ADResult//1000, "psi", 13]

PAUSE 1000

Goto Main

/Henrik.

[richard]

Yeah, deja vu indeed....


I can't make out anything from that datasheet, it's just garbage numbers when viewed on my machine.

/Henrik.

ditto for the pdf
do we have a 54A L07H2210 or a 54ALL07H2210 or a 54AL007H2210 or a 54A 007H2210 ?
they are all different animals and the 54ALxxx are 3.3v devices

[EarlyBird2]

PDF works for me.

The sensor is a 0.07 psi low voltage range with output from 0.5-4.5V

[richard]

that makes it a "54A L07H2210" not what was posted , its best to be sure

steve can you read the characteristics in the data sheet ,that what comes out garbled for me

[EarlyBird2]

'* Notes : For a 18F1320 and 54AL07H2210 *

was it not?

[EarlyBird2]

Is this not a repeat of the left and right output justification as on the previous thread in Richard's link.

7040 left justified is 110 right justified using Henrik's 4.88mV then

110*4.88/1000=0.5368 V

Or put another way 7040/64=110 which shifts the 10 bit left justified result 6 bits to the right making the result the same as a right justified result.