How do you setup a custom table for a 20K ohm thermistor input. I have a table of values for 20k thermistors and have tried numerous times. Any help would be appreciated.
You could build up a table of voltage versus temperature, knowing that the pullup voltage of our controller is a weak pullup through a 10k resistor with 3V excitation voltage. The voltage will be a simple resistor divider formula shown below. Create a spreadsheet with this formula and several representative values for R2 over the temperature range to calculate the associated voltage. Then fill in the results into a custom table. You can see more about custom tables here:
The easier method will be to send us the table of resistances & temperature and Chelsea will add it to the built in tables. While we’re at it I can update this example to show the voltages and custom analog range method above.
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Thanks for your response. I have been trying for several days to set up a table based on temp vs voltage using spreadsheet to calculate. I am new to Temco controls and have just setup and programmed my first controller to replace a failed jace controller. I set up the T3-TB with 10k sensors attached so it worked fine on the bench, but most of our buildings and equipment use 20k ohm sensors.
I found numerous 20k thermistor resistance/temp tables online. But I can send one to you like.
On a side note I was so glad to find Bravo/Temco controllers at a reasonable cost with open source software and no licensing nightmare. I have become so frustrated with proprietary controls with complicated licensing and having to pay thousands to get replacement controls from authorized dealers. I work for a small college where funds and labor are limited, so thanks so much for making the controls available.
| maurice
September 23 |
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You could build up a table of voltage versus temperature, knowing that the pullup voltage of our controller is a weak pullup through a 10k resistor with 3V excitation voltage. The voltage will be a simple resistor divider formula shown below. Create a spreadsheet with this formula and several representative values for R2 over the temperature range to calculate the associated voltage. Then fill in the results into a custom table. You can see more about custom tables here:
Custom analog inputs Input Signals and Configuring
Here’s some screenshots showing how to configure transducers in general. From the inputs table, click in the range column at Tab1 to bring up the range setting dialog with the various sensor types available and select ‘Custom Range’ 50 at Tab2 which brings up another dialog where you set up the signal table. At Tab4 you see the settings to plug in for a typical 4-20ma or 0-10V transducer at the minimum and maximum range of the sensor. You can also type in the engineering units at Tab5. Finally…
The easier method will be to send us the table of resistances & temperature and Chelsea will add it to the built in tables. While we’re at it I can update this example to show the voltages and custom analog range method above.
Thanks for the kind words there WB, I am always surprised when our clients tell us about the cost they are paying in this business, especially with the licensing as you mention. I think we have the 20k in spreadsheet form here somewhere. Chelsea will add it to the stock ranges so you can select them like the 10k and 3k already in there.
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