On a DL06 with an F0-04THM in the first slot, the example program places a temperature value in V2000; the first task is to interpret that value using the same data format and scaling the setup logic uses. A number that looks wrong in DirectSOFT may be a display-format mismatch, not a failed thermocouple.
Read V2000 using the example program's data format
Connect to the PLC in DirectSOFT and open Debug | Change Value. Enter V2000 and inspect its current value while the program is running. That is the first check because the example program identified for this setup stores temperature there.
- Record the value with its current display selection. The reported value near 3500 was viewed with Octal and 4 Bytes selected, so it cannot be compared directly with a temperature in Fahrenheit.
- Check the example program's setup and data-transfer instructions to determine whether the value is handled as BCD or decimal/binary and how many bytes or words are involved.
- Set the DirectSOFT display to match that representation and width, then observe the value again while gently warming the thermocouple.
The replies to this setup differed on whether the value should be read as unsigned decimal or BCD, and explicitly tied that choice to the module setup code. Do not select a display format by trial alone: trace the example logic that transfers or converts the module data. Changing the monitor format only changes how the stored bits are shown; it does not convert the PLC data or change the module configuration.
Confirm the channel wiring before changing ladder logic
The installation described uses two thermocouples on channels 1 and 2 of an F0-04THM in the first slot, with terminals 3 and 4 jumpered as directed by the manual. Compare the actual wiring and module setup against the manual for the installed hardware before treating the example program as a universal template.
With the PLC online, monitor the value associated with the channel being tested. Warm that thermocouple and check whether its reading changes in the expected direction. Then test the other connected channel separately. The evidence identifies V2000 for the example's temperature value, but does not identify the second channel's memory address; use the module's mapping in the manual and the example program rather than assuming an address sequence.
If neither channel responds, stop changing threshold logic. Recheck thermocouple connections, the required jumper, slot placement, module setup instructions, and the example's data-transfer path first. A changing value during the described lighter test showed that the signal path was responding, but it did not establish that the displayed number or temperature scale was correct.
Use the reading format to decide what the number means
Three separate questions determine whether a displayed number is useful: what data representation the PLC stores, what numeric format DirectSOFT is displaying, and whether the temperature uses an implied decimal place. Resolve them in that order.
| Observation | Likely issue to check | Next action |
|---|---|---|
| Value appears around 3500 while Octal and 4 Bytes are selected | The monitor radix and width do not match the intended interpretation | Check the example's data format and view the correct element width and representation |
| Value changes as the thermocouple warms, but does not resemble Fahrenheit | The value may be scaled, such as tenths of a degree, or shown in the wrong representation | Trace the setup logic and check the PID process-variable display |
| Value does not change when the thermocouple warms | Check wiring, channel assignment, setup logic, and module-to-memory transfer before setpoint logic | Compare the installation to the manual and monitor the mapped channel value |
| Channels 1 and 2 show unexpected or identical readings | Channel mapping, channel-specific wiring, or interpretation may be wrong | Test one channel at a time and confirm each mapped value in the example and manual |
A temperature display example in the discussion used 745 for 74.5 degrees and 755 for 75.5 degrees, indicating one implied decimal place for that interpretation. Treat this as a format clue, not a guaranteed scaling for every setup: the setup code controls how the V-memory value is represented. If the PID view is available, inspect its PV (process variable); that view was also suggested as a way to see a temperature with an implied decimal.
Verify the PV scale before entering thresholds
Do not compare a raw number with 150 or 250 until you know what one count represents. First make the monitor and program interpretation agree, then compare the PV with a known temperature indication or a controlled warming response. Check whether the displayed PV includes a decimal place and whether it is in Fahrenheit, as required by the requested thresholds.
If the confirmed representation is tenths of a degree Fahrenheit, 150°F corresponds to 1500 counts and 250°F to 2500 counts. Those comparison values apply only under that labeled scaling assumption. If the PLC value is whole degrees or uses another representation, use the matching threshold values and compare instructions; do not copy 1500 and 2500 blindly.
When DirectSOFT offers different radices or word widths, set these for inspection in a way consistent with the ladder instructions and the data element being monitored. A display setting does not make an incorrect program comparison correct. Keep the raw module data, any conversion result, and the engineering-unit PV distinct when tracing the logic.
Build the 150°F-on and 250°F-off behavior
The requested behavior is a two-threshold, retained-state control: turn Y105 on when temperature reaches 150°F, keep its state between the thresholds, and turn it off when temperature reaches 250°F. Use the correctly scaled PV—not an unverified raw value—in the comparisons.
- Create a set condition when the PV is at or above the confirmed 150°F representation.
- Create a reset condition when the PV is at or above the confirmed 250°F representation.
- Make the two actions mutually exclusive or give the upper-threshold reset priority. At or above 250°F, both numerical comparisons are true; careless rung ordering can otherwise set and reset the output in the same scan.
- Keep the output state unchanged while the PV lies between the thresholds. A simple pair of independent threshold coils that turn off whenever their rung is false will not retain the required state.
For a tenths-of-a-degree PV, use 1500 and 2500 as the assumed comparison values; verify the representation first. Check the DL06 instruction set and the example program for the supported compare and state-control instructions before editing. Test the logic with the output disconnected or otherwise safely inhibited from operating the machine, then confirm that the actual output action is appropriate for the controlled equipment.
Verify the complete path before returning output control
Monitor the channel PV and Y105 together. Raise the measured temperature through the lower threshold and verify that the output turns on once; continue through the upper threshold and verify it turns off. Also check that the output retains its state between thresholds and does not chatter near either boundary. Use a safe test method and do not use an open flame near connected equipment.
After the test, confirm that the running PLC has the intended logic and that the online values match the expected representation, scale, and channel. If a controlled process cannot safely be taken through both thresholds, verify the conditions using an approved simulation or test method rather than forcing a production temperature excursion.
Stop if the PV does not respond, channel mapping remains uncertain, the data representation cannot be reconciled with the setup logic, or the output behaves unpredictably. Preserve the program and readings, then consult the official AutomationDirect documentation or support channel for the DL06 and F0-04THM; do not return the output to service on an unverified scale.
Frequently asked questions
What happens if V2000 shows about 3500?
First check the DirectSOFT display radix and width; the reported value was viewed as Octal with 4 Bytes selected. Trace the example's setup and transfer logic to determine whether the value is BCD or decimal/binary before interpreting it as temperature.
What happens if the temperature value changes but is not in Fahrenheit?
Check the program's data representation and scaling, then inspect the PID PV view if available. A PV such as 745 may represent 74.5 degrees when the setup uses one implied decimal place.
What happens if I use 1500 and 2500 for the setpoints?
Those values are appropriate only if the confirmed PV is in tenths of a degree Fahrenheit. If it is in whole degrees or another representation, scale the comparisons to match the actual PV.
What happens if Y105 turns on and off near a threshold?
Verify the PV scaling and use retained-state logic between the 150°F and 250°F thresholds, with the upper-threshold reset taking priority. Stop and contact official AutomationDirect support if the channel mapping, setup format, or output behavior remains uncertain.