Thermocouple Offset

November 21, 2024
KNOWLEDGEBASE KNOWLEDGEBASE Support> Knowledgebase Thermocouple Offset THERMOCOUPLE OFFSET A thermocouple offset adjusts the kiln’s perceived temperature to achieve the desired temperature. Here’s how it works: Positive Thermocouple Offset: This lowers the kiln's temperature relative to the control's reading. For example, if the control reads 2000°F and you add 10°F of thermocouple offset, the control thinks there is 10°F more in the kiln. Consequently, for a setpoint of 2000°F, the kiln will control to 1990°F. Negative Thermocouple Offset raises the kiln's temperature. For instance, if the control reads 2000°F and you subtract 10°F of thermocouple offset, the control thinks there is 10°F less in the kiln. Thus, for a setpoint of 2000°F, the kiln will control to 2010°F. Avoid having more than 25°F difference between offsets because you might get an E-4 error code. Thermocouple offset adjustments are available on Easy-Fire and custom programs with Dyna-Trol, One-Touch, and Genesis controls. The thermocouple signal determines all temperature readings in your control. Thermocouple readings can be inaccurate due to thermocouple drift or electrical noise (such as inductive current). The most reliable measure you can trust is a witness cone. When you change the thermocouple offset, you are not altering the control's setpoint, only the temperature interpretation via the thermocouple offset. In the offset process, we can think of the control setpoint as a constant, and the thermocouple signal reading as the variable being adjusted. When we add temperature to the thermocouple signal, the control thinks the kiln is hotter than it actually is, causing it to shut off sooner and fire cooler. On the other hand, subtracting temperature from the thermocouple signal makes the control believe the kiln is cooler than it really is, causing it to shut off later and fire hotter. EXAMPLE AND PROCESS Witness cone bent slightly during the first firing, but no more than a little bit -- > Start by reducing the thermocouple offset setting by 5°F to make the kiln fire slightly hotter. Witness cone did not bend at all -- > Start by reducing the thermocouple offset setting by 10°F to make the kiln fire hotter. Witness cone bent a little too much -- > Wait and see how it does with a full load or start by increasing the thermocouple offset by 5°F to make the kiln fire slightly cooler. Witness cone bent more than a little bit -- > Start by increasing the thermocouple offset settings by 10°F to make the kiln fire cooler. If the witness cone collapsed -- > start by increasing the thermocouple offset settings by 15°F. There are beginning suggestions - feel free to experiment outside of this. ANOTHER STARTING POINT METHOD To determine a good starting point for thermocouple offset (or cone offset), you can fire the kiln a cone that is hotter than your witness cone. Then carefully observe when the cone bends and note the temperature displayed on the control. Compare this number with what you think it should be using an Orton Cone Chart. You will have to have some idea of the speed of firing to get an accurate number. THERMOCOUPLE OFFSET - GENESIS Turn kiln ON with toggle switch Press MENU Press # 3- ADJUSTMENTS Press # 2- TC OFFSETS Select TC 1 Enter the degrees you would like to offset your top TC(if negative, make sure to put the "-" symbol before the number) Press SAVE Select TC 2 Enter the degrees you would like to offset your middle TC (if negative, make sure to put the "-" symbol before the number) Press SAVE Select TC 3 Enter the degrees you would like to offset your bottom TC (if negative, make sure to put the "-" symbol before the number) Press SAVE Press BACK to return to the main menu screen THERMOCOUPLE OFFSET - DYNATROL Turn kiln on with toggle switch. Wait 5 seconds. Press 1, wait 5 seconds. The kiln display will say STOP and then go into IdLE mode. Press OTHER about eight times until you see TCOS Press ENTER. See TC 1 Press ENTER again It will flash between °FOS (which stands for Deg F Offset) and 0018 (The 0018 stands for a thermocouple offset of 18°F - which comes preprogrammed into the control to compensate for the ceramic protection tubes. By changing the offset to 0010 we are REDUCING the offset by 8°F- making it fire 8 deg hotter). (NOTE: On older kilns, with a slightly different composition thermocouple protection tube the preprogrammed value is 0050). Press 0008 to reduce thermocouple offset by 10°F. Press 0013 to reduce thermocouple offset by 5°F. Press ENTER to accept your input. Do the same for all your thermocouples. The prompts will scroll past in the order of TC1, TC2 and TC3. THERMOCOUPLE OFFSET - ONE-TOUCH CONTROL Access the Thermocouple Offset by getting into the Options. Options are accessed by holding the ENTER button while turning the power onto the control (turn on the kiln with the toggle switch) and continuing to hold onto the ENTER button until EdIt is displayed. This activates the Options Menu. The first thing you will see after turning the power on while pressing ENTER is LL-G or 1t-1 (This is the software version). Then you will see 1288 if it is a Cone 10 control or 1249 if it is a Cone 6 control. Then you will see EdIt, and you will hear a beep. You can now let go of the ENTER button. Press ENTER again. You will see °F or °C. Press ENTER again, and you will see OFFS Press the UP arrow to enter a positive offset OR press the DOWN arrow to add a negative sign to the offset. All this first button press does is get you in the right range. You can NOW use the UP or DOWN arrow to change the value of the offset. When in the positive range, you can only go as low as 0000. The UP arrow increases the offset setting, and the DOWN arrow decreases it. When in the negative range, you can only go as high as -000. When you are in the negative range, the UP arrow moves the setting in the negative range. For instance, if you start at -000 and hit the UP arrow, you will be at -001 (negative by one degree). If you hit the DOWN arrow, you will go back to -000 (which is actually in the "positive" direction). Some of this is counterintuitive, so it takes some getting used to by just experimenting. Once you are done with your setting, hit ENTER, and in a few seconds, the control will flash between IDLE and some temperature and STOP. If you want to redo the offset setting, turn the control off and start over. Older kilns with closed-end protection tubes came with a pre-programmed +18 Deg F offset to compensate for the thermocouple protection tube. Newer kilns with open-end protection tubes do generally not need an offset (except for fine adjustment). Note that the control does not convert the offset setting to degrees C or F. If you are operating in Degrees C, then the offset setting should be +8 Degrees C. Note: If you first press the DOWN button, you can only set a negative value, or if you first press the UP button, you can only enter a positive value. You can go back and change this later if you make a mistake. ADJUSTING TEMPERATURE VARIATION - TOP TO BOTTOM IN THE KILN Note that you can use different Thermocouple Offsets for the three (or two) different thermocouples. This allows you to make the top or bottom hotter or cooler to even out the temperatures in a kiln.

THERMOCOUPLE OFFSET

A thermocouple offset adjusts the kiln’s perceived temperature to achieve the desired temperature. Here’s how it works:

Positive Thermocouple Offset: This lowers the kiln's temperature relative to the control's reading. For example, if the control reads 2000°F and you add 10°F of thermocouple offset, the control thinks there is 10°F more in the kiln. Consequently, for a setpoint of 2000°F, the kiln will control to 1990°F.
Negative Thermocouple Offset raises the kiln's temperature. For instance, if the control reads 2000°F and you subtract 10°F of thermocouple offset, the control thinks there is 10°F less in the kiln. Thus, for a setpoint of 2000°F, the kiln will control to 2010°F.
Avoid having more than 25°F difference between offsets because you might get an E-4 error code.

Thermocouple offset adjustments are available on Easy-Fire and custom programs with Dyna-Trol, One-Touch, and Genesis controls. The thermocouple signal determines all temperature readings in your control. Thermocouple readings can be inaccurate due to thermocouple drift or electrical noise (such as inductive current). The most reliable measure you can trust is a witness cone. When you change the thermocouple offset, you are not altering the control's setpoint, only the temperature interpretation via the thermocouple offset.

In the offset process, we can think of the control setpoint as a constant, and the thermocouple signal reading as the variable being adjusted. When we add temperature to the thermocouple signal, the control thinks the kiln is hotter than it actually is, causing it to shut off sooner and fire cooler. On the other hand, subtracting temperature from the thermocouple signal makes the control believe the kiln is cooler than it really is, causing it to shut off later and fire hotter.

EXAMPLE AND PROCESS

Witness cone bent slightly during the first firing, but no more than a little bit -- > Start by reducing the thermocouple offset setting by 5°F to make the kiln fire slightly hotter.
Witness cone did not bend at all -- > Start by reducing the thermocouple offset setting by 10°F to make the kiln fire hotter.
Witness cone bent a little too much -- > Wait and see how it does with a full load or start by increasing the thermocouple offset by 5°F to make the kiln fire slightly cooler.
Witness cone bent more than a little bit -- > Start by increasing the thermocouple offset settings by 10°F to make the kiln fire cooler.
If the witness cone collapsed -- > start by increasing the thermocouple offset settings by 15°F.
There are beginning suggestions - feel free to experiment outside of this.

ANOTHER STARTING POINT METHOD

To determine a good starting point for thermocouple offset (or cone offset), you can fire the kiln a cone that is hotter than your witness cone.
Then carefully observe when the cone bends and note the temperature displayed on the control.
Compare this number with what you think it should be using an Orton Cone Chart. You will have to have some idea of the speed of firing to get an accurate number.