Operating instructions

Chapter 4
Ramp-Hold
Before using Ramp-Hold, read all of this
chapter. Have your controller in front of
you so that you can try out the keys as you
read.
Theory of Ramp-Hold Operation
The temperature you are firing to in Ramp-Hold is
called the target temperature. After the Sentry reaches the
target temperature, it can also hold that temperature.
The Sentry 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, Ramp-Hold mode 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 Sentry fires in segments, or stages. A segment is a
controlled heating rate to a target temperature. A segment
can also have a hold. Shown in the chart below is a segment
with a targettemperatureof 1250°, a rate of 625°, and ahold
of one hour.
The two parts of a segment:
I
: The temperature changes.
I
: The temperature remains the same.
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.
A segment can have only one ramp and only one hold.
Therefore, if you need more than one hold, you will have to
add additional segments to the firing. Firing to a tempera
-
ture at a single rate would need only one segment. Reasons
to add more segments:
I
To change the heating rate
I
To add a hold somewhere below the shut-off tempera
-
ture
I
To control the cooling rate.
The diagram below shows a 3 segment firing. Two seg
-
ments were used on the way up in temperature. Another
segment was added for controlled cooling.
To figure how many hours a segment will take to fire,
subtract the current temperature from the target tempera
-
tureand divide the result by theheating rate. Inthe diagram
in the left column, the firing time is 1250° - 80° (room tem
-
perature) = 1170 ÷ 625 = 1.87 hours.
After the Sentry has finished firing the last segment, it
will turn off power to the heating elements.
Storing “User” Programs
To program the controller in Ramp-Hold, must
appear. From press . will appear. The con
-
troller is ready for you to choose a stored program or to en
-
ter a new one. (See next page for programming instruc
-
tions.)
The controller can hold 9 programs in memory. They
stay in memory even when the power is turned off. Stored
programs are numbered 1 through 9. User program 1 can
have up to 20 segments. User programs 2 - 9 can have 10
segments each. You don’t have to use all the segments
available—use only the number needed. Sometimes one
segment is all you will need.
When you program a Ramp-Hold firing, you will be
asked to enter a rate for each segment. Step 7, Program
-
ming Instructions, next page, shows you how to zero out the
segments you don’t need.
When entering a Ramp-Hold program for the first time,
press after appears. Your first firing will be stored
as Program 1.
14 Cone-Fire / Ramp-Hold
Here is a simple 3-segment program. Segments 1 and 2 each have a hold.
Segment 3 is a controlled cooling segment.
This segment will reach the target temperature of 1250° in 2 hours, then
hold that temperature for 1 hour.