Temperature Interface - Revision history

Cartridge1987: /* examples */

2015-11-11T10:54:23Z

examples

2015-11-11T10:54:13Z

accuracy

2015-11-02T11:57:57Z

2015-06-03T13:53:37Z

examples

2015-06-03T13:47:43Z

examples

2015-06-02T15:51:42Z

accuracy

2015-06-02T15:51:09Z

Default operation

2015-06-02T15:50:56Z

Future hardware enhancements

2014-08-27T12:41:58Z

Assembly instructions

2014-08-27T12:39:49Z

← Older revision		Revision as of 10:54, 11 November 2015
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	In practise we often see an error on the order of 5 degrees C too high compared to the ideal temperature reading. We suggest you calibrate at least the offset by doing a reference measurement with a thermometer that you trust. Best would be to electrically insulate the sensor and put it in melting water (0C), and then in boiling water (100C). That way you can calibrate both the offset and gain.		In practise we often see an error on the order of 5 degrees C too high compared to the ideal temperature reading. We suggest you calibrate at least the offset by doing a reference measurement with a thermometer that you trust. Best would be to electrically insulate the sensor and put it in melting water (0C), and then in boiling water (100C). That way you can calibrate both the offset and gain.

	== ~~examples~~ ==		== Examples ==

@@ Line 61: / Line 61: @@
 This is a demo to send things using SPI to the lcd board. The SPI routines there are applicable for the DIO and TEMP boards as well.<br>
-== accuracy ==
+== Accuracy ==
 The sensors claim a +/- 1 or +/- 2 degree accuracy. But the system adds a few more uncertainties. For example, the "internal 1.1V reference" is officially +/- 10%. In practise we've measured it way closer to 1.1 than the range would suggest, but it is a possible source of errors. Similarly, the analog amplifier has an offset voltage that contributes to the overall error.

@@ Line 1: / Line 1: @@
 [[File:Tempic.jpg|thumb|300px|alt=Temperature Interface|Temperature Interface]]
-This is the documentation page for the Temperature Interface
+This is the documentation page for the Temperature Interface. That you can buy in the [http://www.bitwizard.nl/shop/expansion-boards/temp-interface BitWizard shop].
 == Overview ==

@@ Line 71: / Line 71: @@
 The folowing script
  #!/bin/sh
  # Sample script to read and calculate a temperature.
+ #
+ # for I2C:
+ TEMPBRD="bw_tool -I -D /dev/i2c-1 -a 8c"
+ # for SPI:
+ #TEMPBRD="bw_tool -a 8c"
  #
  if [ x"$1" = x"--init" ] ; then
@@ Line 78: / Line 84: @@
    # Channel 0 is first sensor, ... channel 3 is last sensor, sample four channels,
    # add 64 (0x40) samples, and then... don't shift
-   bw_tool -I -D /dev/i2c-1 -a 8c -W 70:81:b 71:80:b 72:82:b 73:83:b 80:4:b 81:40:b 82:0:b
+   $TEMPBRD -W 70:81:b 71:80:b 72:82:b 73:83:b 80:4:b 81:40:b 82:0:b
    # wait for the settings to apply and enough sampes to be taken.
    sleep 1
  fi
- adcconversion=`bw_tool -1 -I -D /dev/i2c-1 -a 8c -R 68:s`
+ adcconversion=`$TEMPBRD -1 -R 68:s`
  # This value is scaled to 65535 is 1.1V.
@@ Line 98: / Line 104: @@
  echo "temperature is: $temp"
 will initialize all four channels if you pass it --init and then read out just the first. On the adcconversion= ... line you need to change to 69 for the second sensor, 6a for the third and 6b for the last.

@@ Line 68: / Line 68: @@
 == examples ==
+The folowing script
+ #!/bin/sh
+ # Sample script to read and calculate a temperature.
+ #
+ if [ x"$1" = x"--init" ] ; then
+   # First initialize the temperature sensor.
+   # Channel 0 is first sensor, ... channel 3 is last sensor, sample four channels,
+   # add 64 (0x40) samples, and then... don't shift
+   bw_tool -I -D /dev/i2c-1 -a 8c -W 70:81:b 71:80:b 72:82:b 73:83:b 80:4:b 81:40:b 82:0:b
+   # wait for the settings to apply and enough sampes to be taken.
+   sleep 1
+ fi
+ adcconversion=`bw_tool -1 -I -D /dev/i2c-1 -a 8c -R 68:s`
+ # This value is scaled to 65535 is 1.1V.
+ # So:
+ # (1)    voltage = adcconversion * 1.1 / 65535
+ # For the MCP9700 temperature sensor:
+ # (2)    voltage = 0.5V + temp * 0.010V/C
+ # Some reworking results in:
+ # (3)    temp = (voltage - 0.5)/0.01
+ # Now we can substitute the voltage from (1) and get:
+ # (4)    temp = 100 * (adcconversion * 1.1 / 65535 - 0.5)
+ # and reworking this we get:
+ # (5)    temp = .001678 * adcconversion - 50
+ temp=`echo $adcconversion \* .001678 - 50 | bc -l`
+ echo "temperature is: $temp"
+will initialize all four channels if you pass it --init and then read out just the first. On the adcconversion= ... line you need to change to 69 for the second sensor, 6a for the third and 6b for the last.
 == Future software enhancements ==

@@ Line 66: / Line 66: @@
 In practise we often see an error on the order of 5 degrees C too high compared to the ideal temperature reading. We suggest you calibrate at least the offset by doing a reference measurement with a thermometer that you trust. Best would be to electrically insulate the sensor and put it in melting water (0C), and then in boiling water (100C). That way you can calibrate both the offset and gain.
-== Default operation ==
 == Future software enhancements ==

← Older revision		Revision as of 15:50, 2 June 2015
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	== Default operation ==		== Default operation ==


	== Future hardware enhancements ==

@@ Line 10: / Line 10: @@
 None: the board comes fully assembled. The orientation of your sensor is indicated on the board, if you use the recommended MCP9700. We suggest you first test with the MCP9700 directly inserted into the socket in the board, before you make an extension cord to put it where you want to measure the temperature.
-Officially electronics should easily be able to handle temperatures of say 80 degrees C, so officially it should be possible to put the whole module where you want to measure. I'd try try to avoid that situation.
+Officially electronics should easily be able to handle temperatures of about 80 °C, so it should be possible to put the whole module where you want to measure. I'd try try to avoid that situation.
 === Possible Configurations ===
 with MCP9700 or LM35. If you know of other sensors that provide a similar signal, let us know.
 == External resources ==

← Older revision		Revision as of 12:39, 27 August 2014
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	[[File:.jpg\|thumb\|300px\|alt=\|]]		[[File:Tempic.jpg\|thumb\|300px\|alt=Temperature Interface\|Temperature Interface]]

	This is the documentation page for the Temperature Interface		This is the documentation page for the Temperature Interface