Setting Up the Fuji PXV3 and PXZ Temperature Controllers
by Roger Peterson

In recent months several glass workers on the Glass Line email list have purchased a new variety of temperature controller manufactured by Fuji Electric. This equipment has many of the features that you find on more expensive controllers from traditional manufacturers.

As is the case with most controllers in this business, the ones manufactured by Fuji are somewhat of a challenge to initially set up. This is a result of the manufacturer providing a large selection of built in parameters and optional features which allow the user to tailor the controller to the widest range of applications. In the process of setting up both the low cost PXV3 series and the PXZ series controllers for use with an annealer and a glass furnace, much was discovered about the design and capabilities of these controllers. This information is being provided as supporting documentation to Fuji's extensive "Operation Manual". Each user should read and refer to this manual for the details of installation and operation of these controllers.

Before changing any parameters, make sure that power to the furnace/annealer is unplugged. You only want power to the controller until you are ready to test the changes you have made.

Parameter Masks

Out of the box, the Fuji controllers will allow you to select a single setpoint and start controlling your process. But Fuji may not have enabled all of the parameters necessary for taking advantage of more advanced features such as ramp/soak programming. These and all other features are made available by programming the parameter masks.

Perhaps the hardest concept to master in the world of computers is that of parameter masks. It is usually very clear when a manual tells you to set the thermocouple type to a particular value for your application, but what's a mask? And more importantly, is it set or cleared to do the particular action you want?

First a mask is a computer designer's way of storing individual bits in a data word used to indicate whether to enable or disable a particular feature. By setting or clearing a specific bit in a data word, each feature or parameter can be enabled or disabled by the user.

But which is it? Do you set the bit to enable the feature, or do you clear it? This small piece of information is usually left for the reader to experimentally determine. In the case of the Fuji controllers, setting the bit in the mask disables that particular parameter.

Given the number features are available in these controllers, how many programmable masks are required? In this case Fuji provides seven, 8-bit words. They are called "dsp1" through "dsp7" and the case of the PXV3 controller are accessed through the "Factory Preset Menu". The same settings are accessed through the "Secondary Menu" on the PXZ series controllers. (As a bit of technical trivia, I suspect the terminology "dsp" refers to "digital signal processor". This is a specialized technology used in low-cost, high-volume electronics.)

One can see that 56 parameters are potentially available. True, but not all of these parameters are of interest to us and some may not apply to the particular model of Fuji controller you are using. First let's look at how these parameter bits are organized. In the following tables, each parameter is laid out in its correct position in the data word. At the top of each column is the decimal value of each bit. The abbreviations used are those found in the Fuji manuals.

Table 1, Fuji PXW/PXV3 Controller

* "ProG" is not displayed on the PXV3 menu. "oFF" or "rUn" or "HLd" are shown.

Table 2, Fuji PXZ Controller

Note that bits for comparable parameters in each type of controller are located in dramatically different positions! And yes in each case, three of the 56 bits are not used. This is all to keep us bit-mavens on our toes.

Now how do you go about using all this information? Each dsp word can contain any value from 0 to 255 — or from enabling all of the parameters associated with the word, to disabling all of them. Let's take and example using the table for the PXV3.

The PXV3 does not have the heater break option (Hb) available as an option and alarm outputs (AH and AL) must be purchased as optional equipment. If we want to mask those bits so they do not show in the menu we would set,

dsp1 = 8 + 4 + 2 = 14.

All other parameters (P, LoC, AT, and oFF or rUn or HLd) would display and could be changed normally. Keep in mind the number you are entering into a particular dsp word is expressed in decimal. It represents the bit positions you want to mask — i.e. disable.

There is one side effect of this procedure. Those bits related to the parameters used for programming the ramp/soak feature may be enabled or disabled as you wish. If a setpoint value (SV-1 through SV-4) is disabled, the program will skip over that step in the program. In the limit, if you just wanted your program to ramp to a preset temperature and then hold there, you could mask all of the programming parameters except TM1r and SV-1. There will be more to say about this in the section on programming.

Setting Parameters for Controlling a Furnace or Annealer

With dsp masks set, we can now access all the necessary parameters required for setting up the controller to operate properly. The first that needs our attention is "P-n2" the parameter that sets the input. As shipped the factory may have set this code to a different thermocouple than your are using. For annealers you will most likely use a Type-K TC which requires P-n2 = 3. For high temperature furnaces you might be using a Type-R TC which requires P-n2 = 4. Consult the "Table of Input Codes" in your manual to make sure you select the correct code.

You will then want to set the following parameters.

Table 3, Fuji Control Parameters

Notice we skipped over parameters such as P, I, D, and Ar and the command AT. This because these are the control parameters that get set automatically when the system is set to auto-tune (AT = 1).

After these parameters are set, the system should be reconnected and the power turned on. For annealers or furnaces, the setpoint (SV) should be set to about 500°F or 250°C. After the furnace has reached the setpoint, you should select AT and set the data equal to one. At that point the controller takes over and automatically determines the control algorithm parameters. A tiny indicator should flash in the lower right corner of the display while this is taking place. Consult the manual if this does not happen or an error occurs.

After successfully establishing the control parameters, select FUZY and set it on. You may turn off the furnace or continue controlling while new ramp/soak parameters are set in the controller.

Programming the Ramp/Soak Feature

Programming any computer driven device can be intimidating, but Fuji has removed most of the challenges from this process. In fact their explanation and drawing in the manual is very descriptive and will not be repeated here. A few notes may help clarify some of your remaining questions.

First note that the setpoint value is reached at the end of the associated ramp. That is to say, the sequence of events is,

1. Start a timed ramp, TMxr, from the present temperature to the next setpoint, SV-x.
2. Soak at that temperature for TMxS minutes and seconds.
3. Go to the next ramp or end the program.

Note that each active setpoint must be set to a temperature of your choosing. Any or all setpoints may be deactivated (removed from the program sequence) by setting the appropriate dsp mask.

What Happens at the End of a Program?

Finally we get to the end! If all has been set up and programmed correctly, Fuji controllers will continue controlling at the last setpoint indefinitely. If this is not the case, the following can be used as a start to trouble shooting.

1. Assuming no error conditions are displayed, check that STAT=end. If this is not the case, the program is still running. Consult the manual for the meaning of the data displayed in the STAT parameter.
2. If the program is at the end, but the temperature is dramatically different than expected, check the value of the last programmed setpoint – usually SV-4. The last SV executed must be set to your desired temperature.
3. If the last programmed setpoint is ok, but the temperature commanded is different than expected, check the value of the MOD parameter. Perhaps MOD is set to a value for leaving the controller in standby when the program ends. (MOD would most likely equal 4, 5, 6, 7, 12, 13, 14, or 15.) It is strongly suggested that MOD be set to zero until the user becomes familiar with the operation of the Fuji controller.
   
   If the controller is in standby mode, the output temperature will be set to 3% below the last commanded setpoint.

If you want to regain control of the main sepoint (SV), you must set the program to oFF. Doing so will terminate the program and immediately change the commanded setpoint to its original value stored before the program executed. You can use the up/down arrows to change this main setpoint as needed.

The Final Word

When all else fails,

Persevere ! !

(From Ed Schmid, Advanced Glassblowing Techniques)

Version 1.0, 8/6/99

© 1999 R. Peterson, California Glassmith