Sentry Industries Sentry Xpress 4.0 manual Theory Operation, Rate, Hold

Theory of

Operation

The temperature you are firing to is called the target temperature. After the controller reaches the target tem- perature, it can also hold that temperature.

The controller fires at a controlled heating rate. The rate is figured in degrees per hour. If you selected a rate of 100° per hour, it would take 10 hours for the kiln to reach 1000°. Rate is similar to “miles per hour.”

In summary, the controller does three basic tasks:

1)It fires at a controlled heating rate, or speed, mea- sured in degrees of temperature change per hour.

2)It fires to a target temperature.

3)It can hold the target temperature.

The controller fires in segments, or stages. A segment is a given heating rate to a target temperature. Shown above is a segment with a rate of 625° per hour, a target temperature of 1250°, and a hold of one hour.

Heating rate is figured in degrees per hour. The recom- mended heating rate for the material you are firing is usu- ally available from your supplier. It also varies depending on the thickness of the material.

To figure how long a firing segment will take, subtract the current temperature from the target temperature and divide the resultant temperature by the heating rate. In the diagram above, the firing time is 1250° - 80° (room tempera- ture) = 1170 ÷625 = 1.87 hours.

The controller can fire up to 8 segments per firing. One segment is often all that is needed, though.

After the controller has finished firing the last segment, it will turn off power to the elements.

Note: If you enter a rate of 0000 in segment 1, or if the target temperature in segment 1 is lower than the cur-

rent temperature, will appear in the display.

Rate

Each segment must include a rate, which is degrees of temperature change per hour.

The kiln will fire at full power when the rate is

1799°F/999°C. Full power displays as .

Note: To enter full power from		, press the
	key once.

Hold

Hold is the length of time that you want the kiln to re- main at the target temperature. Hold is also called soak or dwell time. Hold maintains a steady temperature for the length of time you specify. You can use Hold in both heat- ing-up and cooling-down segments.

When Hold is set to 99.59 hours, the controller will re- main at that temperature indefinitely, until you press

. To enter a 99.59 hour Hold, press the once from 00.00 during programming.

Note: During a Hold, the display flashes between the Hold temperature and time left in Hold.

Two Firing Modes: Single-Speed and Ramp-Hold

To give you greater flexibility, your controller has two firing modes:

Single-Speed Mode (see next page)

Often times, all you will need is Single-Speed mode, which has one segment that includes a rate (temperature change per hour), a target temperature, and (if needed) hold time.

In Single-Speed mode, you can choose one of five firing speeds. Then enter the temperature you are firing to.

Ramp-Hold Mode (see page 7)

Ramp-Hold mode offers much greater flexibility than Single-Speed mode. Use Ramp-Hold to create custom fir- ings with up to 8 segments. The controller can store 4

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