I have a problem with the readadc10 command giving me some wierd values on my 28X1.
The circuit, powered by 12V DC battery supply, is a AD595AQ (K Type Thermocouple Amp IC) connected to the 28X1 (with a RC filter on the amp output pin 9). The PICAXE code performs the readadc command on this "10mV per degC" voltage signal and displays the readc10 Word on an LCD.
Using a DVM, the output from the AD595 is a steady eg. 172.6mV (not seeming to fluctuate any more than +/-0.3mV). Reference / Supply Voltage is 5.04V (not fluctuating any more than +/-10mV) via an 7805 voltage reg.
When I run the readadc10 in a loop and display it's result every 200ms on the LCD it displays a rsult of anywhere between 26 & 36.
A voltage of 172.6mV should be getting a steady 35 (172.6mV / 5040mV * 1024). A range of between 26 & 35 would indicate that the voltage is ranging from ~128mV to ~173mV but my multimeter shows that it's a steady 172.6mV
Can noise in the circuit affect the readadc10 so much? What in the circuit should I be changing to get rid of thoise noise??
Circuit I'm using : http://www.mearcat.com.au/images/TC_Cct.jpg
-Alan
Edited by - mearcat on 23/08/2007 04:39:20
Edited by - mearcat on 23/08/2007 04:39:51
The circuit, powered by 12V DC battery supply, is a AD595AQ (K Type Thermocouple Amp IC) connected to the 28X1 (with a RC filter on the amp output pin 9). The PICAXE code performs the readadc command on this "10mV per degC" voltage signal and displays the readc10 Word on an LCD.
Using a DVM, the output from the AD595 is a steady eg. 172.6mV (not seeming to fluctuate any more than +/-0.3mV). Reference / Supply Voltage is 5.04V (not fluctuating any more than +/-10mV) via an 7805 voltage reg.
When I run the readadc10 in a loop and display it's result every 200ms on the LCD it displays a rsult of anywhere between 26 & 36.
A voltage of 172.6mV should be getting a steady 35 (172.6mV / 5040mV * 1024). A range of between 26 & 35 would indicate that the voltage is ranging from ~128mV to ~173mV but my multimeter shows that it's a steady 172.6mV
Can noise in the circuit affect the readadc10 so much? What in the circuit should I be changing to get rid of thoise noise??
Circuit I'm using : http://www.mearcat.com.au/images/TC_Cct.jpg
-Alan
Edited by - mearcat on 23/08/2007 04:39:20
Edited by - mearcat on 23/08/2007 04:39:51