Here are some basic connection schematics for the picolog 1000 and ADC-20/24.

Setup on Channel 1. NOTE for the ADC20/24- If you are going to use more than one NTC you will need to use external 2v5 supply reference. (The ADC-20/24 onboard 2v5 rail is rated for 2mA)

NTC's have a non linear resistive response to temperature.

There two methods that can be used to calculate temperture-

-Use a lookup table in the form of a scaling file in picolog

-Or use equations with the use of the 'calculate parameters'

**Example of using equations with the use of picologs 'calculate parameters'**

Hardware setup (As above)-

Using the ADC-24, with 10K thermistors wired in series with 6.49K Ohm resistors, connected to the 2.5v reference.

Here's the method and equations, which uses the Steinhart-Hart equation with modifications to reduce the dynamic range of values required.

As channels calculates are limited to 8 digits and 5 decimal places.

Doing the linearisation for each thermistor uses three calculated parameters.

1. Compute natural log of thermistor resistance as first calculated parameter

Code: Select all

`LnR1 = ln ( Rseries * ( A / ( 2500 - A ) ) )`

where Rseries is the series resistor in this case 6.49K Ohms.

2. Compute the inverse temperature times 10,000 as the second calculated parameter

Code: Select all

`InvT1 = ( ( ( ( ( 8.863 * A * A ) / 100 ) + 233.9 ) / 100 ) * A ) + 11.303`

3. Compute the temperature as the third calculated parameter

Code: Select all

`Temp1 = ( 10000 / A ) - 273.15`

You download the example settings file here- This is setup for the ADC-20 with above circuit.