AutomationDirect Logo Process Control Frequently Asked Questions

 

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Question: What is a limit controller?
Answer: Limit controllers are a specific type of process or temperature controller whose alarm outputs latch when energized and must be manually reset. We don't sell any limit controllers, although we do carry on/off controllers whose main difference is the outputs do not latch.
FAQ ID: 913

Question: Why must a controller be tuned and if so when?
Answer: Process controllers must be tuned because no two processes are alike. What works for one will not necessarily work for another. Tuning can be performed anytime an installation occurs, new component installed, or anytime the installers feels that better performance can be obtained. It’s solely up to the end user and the process that is being controlled.
FAQ ID: 914

Question: Do you sell a 24VDC version of the PM24, TC33, PC35, or Solo controllers?
Answer: The power requirements for the PM/TC/PC units are 90-260VAC. The Solo controllers are powered by 100-240VAC. There are no plans at this time to carry a DC powered unit.
FAQ ID: 915

Question: What is the input sampling rate?
Answer: PM24 – 10 per second (100ms) TC33 – 10 per second (100ms) PC35 – 10 per second (100ms) SOLO: Thermocouple input: 400ms per scan Platinum RTD: 400ms per scan Analog: 150ms per scan
FAQ ID: 916

Question: Can the units communicate to external devices?
Answer: The PM/TC/PC controllers don't have any communication capability. The Solo controllers can communicate via RS-485 Modbus RTU or Modbus ASCII protocol as Modbus slaves. We offer free software to use with these controllers to monitor or set them up via a PC, but you will have to convert the RS-485 signal to something your PC can use (typically RS-232).
FAQ ID: 917

Question: How can I set the controller to on/off control?
Answer: On the TC33 and the PC35 need to have the Pb (Proportional band) to 0. The PM24 is only an on/off controller. The Solo controllers have a parameter, CTRL, which you use to select the control mode, either PID, ON/OFF, MANUAL, or PROGRAM (for ramp/soak).
FAQ ID: 918

Question: How do I change from F to C degrees?
Answer: PM24 and TC33 – cycle 3 and unit PC35 – cycle 5 and unit. Solo: If the input type is a thermocouple or RTD, the TPUN parameter lets you select either F or C.
FAQ ID: 919

Question: Why does the temperature go down instead of up when the heat is applied?
Answer: You have the sensor leads reversed.
FAQ ID: 920

Question: What is a PID/Process controller?
Answer: This type of feedback controller has a single-loop (one channel of control) and utilizes a PID (proportional-Integral-Derivative) control algorithm. The output (control variable or CV) of this controller is based on the error created by a user defined set point (SP) and a process measurement (process variable or PV). The PID algorithm defines how each element acts on the error signal created. Proportional – the proportional term simply responds proportionally to the current size of the error. The loop controller calculates a proportional term value for the PID calculation. When the error is zero, the proportional term is also zero. Integral – the integral (or reset) term integrates (sums) the error values. Starting from the first PID calculation after entering auto-mode, the integrator keeps a running total of error values. The running total represents the constant output required to hold the current PV. Derivative – the derivative (rate) term responds to change in the current error value from the error used in the previous PID calculation. Its job is to anticipate the probable growth of the error and generate a contribution to the output in advance.
FAQ ID: 921

Question: When I press and hold the "setup" key on the PC35 to configure the controller, the display flashes between settings. Why does it flash?
Answer: The "setup" key must be used in conjunction with the "back" key. This allows the user to step through all of the cycles. The flashing is an indication that an illegal operation has been performed.
FAQ ID: 923

Question: How many feet of thermocouple wire can I use?
Answer: There is an input limitation of >10Mohms impedance for the PM/TC/PC controllers and >4.7M for the Solo controllers. Review the specifications of the thermocouple wire (diameter, distance, material, etc.) to make a determination of distance limitations. If the environment is electrically noisy or the run exceeds the limitations of the controller, then a transmitter can be used to boost the signal and convert it to a 4-20 ma input (in which case a TC33 cannot be used because of no 4-20 ma input.)
FAQ ID: 926

Question: What is retransmission on the PC35 controllers?
Answer: It is the exact 1-1 ratio of the input retransmitted to other controllers or chart recorders.
FAQ ID: 927

Question: How should I wire your RTD0100 series of RTDs to the FC-R1 RTD signal conditioner?
Answer: The RTD0100 series is our four wire RTDs. Two each of the wires are connected to each side of the RTD. PIN # WIRE COLOR 1 BROWN 2 WHITE 3 BLUE 4 BLACK So for our RTDs, BROWN and WHITE are connected to the same point on the RTD and BLUE and BLACK are connected to the other point. The RTD input of the FC-R1 has three connections: + (plus), - (minus), and COM. In order to wire our four wire RTD to the FC-R1 input, one of the wires should remain disconnected on the RTD0100 cable. The other wire that connects to the unused wire on the RTD is the wire that should be connected to the + (plus) terminal of the FC-R1. As an example, if you don’t use the BROWN wire in the RTD0100, then the WHITE wire should be connected to the + (plus) terminal. The other two wires, BLUE and BLACK in this example, should be connected to the – (minus) and COM terminal. It does not matter which color is connected to which terminal for these two wires. To restate the example, don’t connect the BROWN wire of the RTD0100 to anything. Connect the WHITE wire to the + (plus) terminal of the FC-R1, connect the BLUE wire to the – (minus) terminal, and the BLACK to the COM. This will properly connect the RTD0100 to the FC-R1. Other combinations can be wired and be correct, but this is an illustration of one combination. If you need to extend the wire for the RTD run, we recommend Belden 8403 or equivalent.
FAQ ID: 1266

Question: Can the SOLO Ramp/Soak function be turned on remotely from an external input?
Answer: Yes. If you use the SOLO 4896 or 9696 models you can use Event Input 1 to enable or disable your Ramp/Soak operation. If Event Input 1 is closed ( a contact is closed between terminal #3 SG and terminal #4 Ev1) the output will be disabled and the Ramp/Soak operation will cease its operation. Upon opening the contact between SG and Ev1 the Ramp/Soak will start its operation again at Step 0. It will not resume operation of the Ramp/Soak table from the point the contacts were closed.
FAQ ID: 1267