Pid Trainer

DirectLOGIC PID ,[object Object],BEGIN SETUP TROUBLE- SHOOTING

Initial Setup … ,[object Object],[object Object],[object Object],[object Object],[object Object]

… initial setup ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],V-Memory Ranges Max Loops Per CPU

Configure Details Minimum Requirements … ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Basic Setup … SP/PV ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],SP/PV Details

Basic Setup … Output ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Output Details

Basic Setup … Tuning ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Tuning Details

Basic Setup … Alarms ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Alarm Details

Basic Setup … R/S ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Basic Setup … Complete ,[object Object],[object Object],[object Object],[object Object]

Starting the PID ... ,[object Object],[object Object],[object Object]

Viewing the PID ... ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],P I D System in Operation …

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Ladder Code ...

Position -vs- Velocity … Configure Details ,[object Object],Algorithm: Transfer Modes: SP/PV & Output Format: Loop Mode: Sample Rate Forward -vs- Reverse Common -vs- Independ. Unipolar -vs- Bipolar 12-bit 15-bit 16-bit BMP I -vs- BMP II Independ. of CPU Configure Tab Alarms Details SP/PV Details Output Details Tuning Details

… SP/PV Details ,[object Object],SP/PV Format: Common -vs- Independ. Unipolar -vs- Bipolar 12-bit 15-bit 16-bit Set Point: Address Process Variable: Address Remote SP Pointer Enable Limiting Square root Auto Transfer Configure Details Alarms Details SP/PV Tab Output Details Tuning Details

Address … Output Details ,[object Object],Output: Limits Auto Transfer Output Format: Common -vs- Independ. Unipolar -vs- Bipolar 12-bit 15-bit 16-bit Configure Details Alarms Details SP/PV Details Output Tab Tuning Details

-P- Proportional Gain … Tuning Details ,[object Object],Gains & Bias: Limits & Errors: -I- Integral Gain -D- Derivative Gain Freeze Bias Error Sq. Enable Deadband Derivative Gain Limiting Configure Details Alarms Details SP/PV Details Tuning Tab Output Details Bias

… Alarm Details ,[object Object],Limit Alarms: Alarm Hysteresis: Alarm Hysteresis Rate of Change: Monitor Rate of Change Configure Details Tuning Details SP/PV Details Alarms Tab Output Details PV Deviation: Enable PV Deviation Limit Alarms

Algorithm : ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Sample Rate: ,[object Object],[object Object],[object Object],[object Object],[object Object]

Forward/Reverse Acting: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Bumpless Transfer Modes: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Common -vs- independent: ,[object Object],[object Object],[object Object]

Unipolar -vs- Bipolar: ,[object Object],[object Object],[object Object]

12-15-16-Bit Resolution: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Limit Alarms: ,[object Object]

Monitor Rate of Change: ,[object Object],[object Object],[object Object],[object Object],[object Object]

PV Deviation: ,[object Object],[object Object],[object Object]

Alarm Hysteresis: ,[object Object],[object Object],[object Object],[object Object]

Proportional Gain: ,[object Object],[object Object],[object Object],[object Object]

Integral Gain: ,[object Object],[object Object],[object Object]

Derivative Gain: ,[object Object],[object Object],[object Object],[object Object],[object Object]

Freeze Bias: ,[object Object],[object Object],[object Object],[object Object],[object Object]

Bias: ,[object Object],[object Object],[object Object],[object Object],[object Object]

Derivative Gain Limiting: ,[object Object],[object Object],[object Object],[object Object]

Error Squared: ,[object Object],[object Object]

Error Deadband: ,[object Object],[object Object],[object Object]

Output Address: ,[object Object],[object Object],[object Object],[object Object],[object Object]

Output Limits: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Auto Transfer to Output module: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Set Point Address: ,[object Object],[object Object],[object Object],[object Object],[object Object]

Process Variable Address: ,[object Object],[object Object],[object Object],[object Object],[object Object]

Remote SP Address Pointer: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Enable Limiting: ,[object Object],[object Object],[object Object],[object Object]

Auto Transfer from Input module: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Square Root: ,[object Object],[object Object]

Independent of CPU mode: ,[object Object],[object Object],[object Object],[object Object]

Terms: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Troubleshooting ,[object Object],No Output: Output Limits P-I-D Values Time Proportion Control Will not switch to AUTO: Ladder Code CPU not in RUN Remote SP Pointer Incorrect or No SP/PV values: BCD to BIN SP Limits PV Auto X-fer Algorithm Auto Manual Ladder Code CPU not in RUN Output Auto X-fer Ramp Soak Sample Rate BEGIN SETUP

No Output ,[object Object],In the Output Tab of the PID setup, you will see an Upper and Lower Limit. Verify that the upper limit has been set to a value greater than zero. An Upper Limit of zero will cause the PID to think it has reached it’s maximum value before it gets started. In cases where the output value needs to be restricted, it may be best to leave these limits at the output full range (ex. 0-4095 for 12-bit) and scale them in the ladder code.

No Output ,[object Object],In the Tuning Tab of the PID setup, you will see the Proportional, Integral & Derivative gains. To get an output from the PID algorithm, you must have a value in at least one of these variables. You can also set these values from the PID View window. From here you can set and adjust the values while your process is running. This will allow you to manually tune the loop. In many cases you may only need one or two of the variables set to obtain the loop control that your process requires. P-I loops are among the more common process control configurations seen. What combination is best for your application? This can ONLY be determined by running the process to see how it will react.

No Output ,[object Object],In the Configure Tab of the PID setup, you have the option to select Position -vs- Velocity algorithm as well as Forward Acting -vs- Reverse Acting. 90% or more of the applications that we have encountered are Position Algorithm. If your process is designed for one and you have the other selected you can expect to get unpredictable results at best. Forward & Reverse Acting loops are defined differently by different people. Make sure you understand the meaning of each before selecting one for your process. Forward Acting is also referred to as a ‘heating loop’ where Reverse acting may be referred to as a ‘cooling loop’.

No Output ,[object Object],In the Configure Tab of the PID setup, you will see a selection for Independent of CPU mode. If this is not selected the CPU must be in RUN mode before the PID will function. Typically this is not selected because you will need the processor in run to adequately filter the inputs from the process into the PID and allow the PID output to effect the process. There are cases where the PID does need to operate even if the rest of the process is not active. This is really the only reason for the Independent mode to be selected.

No Output ,[object Object],The mode of the PID loop can cause the Output not to function. You can set the PID mode through the PID View or in the Ladder code. The ladder code ALWAYS takes precedence over any manual changes you try to make. In Manual mode the Output will hold it’s last state. This is the only mode which will allow you to actually write a value to the Output V-memory location. Manual mode is set by V+00 bit 0. Auto mode is the common operating state of the PID loop. In this mode the Output is determined by the PID algorithm. Auto mode is set by V+00 bit 1

No Output ,[object Object],The ladder code ALWAYS takes precedence over any manual changes you try to make. Check the ladder code to verify that the PID Output, V+05, is being written to the correct output channels for your process.

No Output ,[object Object],If you are using Time-Proportioning Control, also known as on/off control, then you will need to verify that the programming code has been entered into the ladder. You can find an example of this on page 8-52 of your USER manual. (pages may vary depending on manual and manual revision)

No Output ,[object Object],In the Output tab of the PID set you will find the option to select the auto transfer to I/O module. If this has been selected you will need to removed any analog module setup in your current code AND CPU memory. Auto transfer is one of many options for telling the CPU how to write data to the analog output modules. You can only use one method at a time. If you had previously been using the pointer method for setting up analogs in the 05, 06, 205 or 350 CPU’s, the pointer setup may remain in the CPU memory even if you remove the setup code from the ladder. You will need to clear the corresponding V-memory ranges before the auto transfer will function. Take into consideration that if you select the auto transfer that you can NOT use these other programming methods for the analog cards and this may restrict the use of the remaining channels.

Will not switch to AUTO ,[object Object],The ladder code will switch the PID mode by setting the appropriate bit. V+00 bit 0 for Manual and V+00 bit 1 for Automatic. If you are trying to change the PID mode from the PID View and it will not, chances are that the code is telling it to do something else. The PID is running asynchronies to the CPU scan. Therefore, it is possible for the PID to not see a mode request change in one CPU scan. Page 8-20 of the USER manual shows an example of how we recommend you change the modes. By using a Store Positive Differential (one shot contact) to energize a SET coil of the appropriate mode bit, we guarantee the PID to see the bit go high and the PID will in turn reset the mode bit for you. (pages may vary depending on manual and revision)

Will not switch to AUTO The ladder code will switch the PID mode by setting the appropriate bit. V+00 bit 0 for Manual and V+00 bit 1 for Automatic. If you are trying to change the PID mode from the PID View and it will not, chances are that the code is telling it to do something else. The PID is running asynchronies to the CPU scan. Therefore, it is possible for the PID to not see a mode request change in one CPU scan. Page 8-20 of the USER manual shows an example of how we recommend you change the modes. By using a Store Positive Differential (one shot contact) to energize a SET coil of the appropriate mode bit, we guarantee the PID to see the bit go high and the PID will intern reset the mode bit for you. (pages may vary depending on manual and revision) ,[object Object],In the Configure Tab of the PID setup, you will see a selection for Independent of CPU mode. If this is not selected the CPU must be in RUN mode before the PID will function. Typically this is not selected because you will need the processor in RUN to adequately filter the inputs from the process into the PID and allow the PID output to effect the process. There are cases where the PID does need to operate even if the rest of the process is not active. This is really the only reason for the Independent mode to be selected.

Will not switch to AUTO ,[object Object],The Remote Set Point Pointer is ONLY used for Cascade mode operation. If there is a Remote set point pointer selected, the loop is looking for the Cascaded loop to be in auto mode also. If it does not see the this it will not allow this loop to function. The Major loop of the cascaded pair will not go into Auto mode unless the Minor loop is in Cascade mode.

Will not switch to AUTO ,[object Object],The Sample Rate determines how often the PID loop is updated. If you have a long scan time, it may take the PID a while to recognize that you have requested a mode change.

Incorrect or no SP/PV values ,[object Object],The data type of the values being written to the Set Point and the Process Variable is an area where oversights are commonly made. The data type of these variables is required to be in Binary format for the PID algorithm. The default data type for all of our processors is BCD. Therefore, it is required that you convert these values from BCD to BIN before writing the data to the PID loop. See page 8-8 of the USER manual for the Loop Table Word Definitions. This gives you a column that specifies the data type for each word.

Incorrect or no SP/PV values ,[object Object],In the SP/PV tab of the PID setup, you will see a selection for ‘Enable Limiting’. This allows you to place upper & lower limits on the Set Point variable. If the limits are inadvertently set to values that are not within the boundaries of the possible set point entries, you will see the entered values being overwritten.

Incorrect or no SP/PV values ,[object Object],In the SP/PV tab of the PID Setup, you will find the option to select the auto transfer from I/O module. If this has been selected you will need to removed any analog module setup in your current code AND CPU memory. Auto transfer is one of many options for telling the CPU how to read data from the analog input modules. You can only use one method at a time. If you had previously been using the pointer method for setting up analogs in the 05, 06, 205 or 350 CPU’s, the pointer setup may remain in the CPU memory even if you remove the setup code from the ladder. You will need to clear the corresponding V-memory ranges before the auto transfer will function. Take into consideration that if you select the auto transfer that you can NOT use these other programming methods for the analog cards and this may restrict the use of the remaining channels.

Incorrect or no SP/PV values ,[object Object],If a Ramp / Soak table has been set up and enabled, it now has control of the set point. You would be able to write to this value between steps, but it will revert back to the presets on the next ramp step.

[object Object],[object Object],** Finished ** BEGIN SETUP TROUBLE- SHOOTING

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