Operating instructions

Frequently Asked
Questions
Does the increase in Ramp-Hold temperature
assume a one hour time period?
Yes. When you program the rate, you are telling the
controller how much the temperature needs to go up or
down per hour. A car’s speedometer measures speed in
miles or kilometers per hour. To understand temperature
rate, think of a speedometer that measures temperature
change per hour instead of miles. This applies to both heat
-
ing and cooling rate. At a rate of 100 degrees per hour, the
kiln would take 10 hours to reach 1000 degrees.
It may be easier to understand the controller by drawing
your program on graph paper. Show slanted lines for rates
and horizontal lines for temperature holds.
When a digital kiln is taking longer than usual to
complete a firing, how do you know whether
something has gone wrong and the kiln is
over-firing?
You should place pyrometric witness cones on the shelf
so that you can see them through a peephole (page 10).
Another way to prevent an over-fire is to learn to esti-
mate kiln temperature by the color of light showing around
the lid and peepholes.That way, youcan tell at aglanceif all
is well with your kiln. You could also use a pyrometer as a
temperature reference.
Does the room temperature affect the accuracy of a
digital controller? (For instance, does the controller’s
temperature change from summer to winter in an
unheated building?)
The Sentry controllers compensate for room tempera-
ture as long as you stay within the range of 32°F – 158°F
(0°C - 70°C). For instance, if your unheated room is 32°F /
0°C in the winter and 100°F / 38°C in the summer, the room
temperature should have no effect on the way the control
-
ler reads the kiln’s firing chamber.
I fire ceramics. When would I ever need to use
Ramp-Hold mode instead of Cone-Fire?
Most people use Cone-Fire mode to fire ceramics. It is
simple—just enter speed, cone, and hold time. Ramp-Hold
mode, by comparison, seems complicated. Ramp-Hold di
-
vides the firing into segments, each with a rate, target tem
-
perature, and hold time.
But some people fire all their ceramics with Ramp-Hold
instead of Cone-Fire. Their reasons:
1) If the witness cone doesn’t bend to maturity (page 20)
in Cone-Fire, you can adjust the shut-off point in the next
firing by adding hold time or using the Cone Offset option
(page 20).
To adjust a Ramp-Hold firing to make the witness cone
bend to maturity, just alter the target temperature of the
segment that fires the cone tomaturity. That issimpler than
correcting a Cone-Fire firing.
For example, thewitness cone on the shelfneeds to bend
just a little farther. Merely add 10 degrees of temperature
rise to the next Ramp-Hold firing. Instead of programming
a target temperatureof 2232° F for cone6, program2242°F.
If the witness cone is bent slightly too far, you can easily
back off 5 or 10 degrees the next time.
2) The Sentry includes candling and slow-cool in
Cone-Fire mode. Candling helps dry the greenware;
slow-cool gives certain glazes extra time for full develop
-
ment. In Ramp-Hold, you canprogram candling, slow cool
-
ing, and other features merely by adding more segments.
3) You learn more about firing when you program each
step yourself.
4) You can experiment in Ramp-Hold more than you
can in Cone-Fire. Ramp-Hold simplifies the firing of diffi
-
cult glazes such as crystalline. If a friend or teacher gives
you the firing schedule for a glaze, you can modify it easily
in Ramp-Hold to obtain the best results for your kiln and
materials.
Why does my controller begin the next segment even
though the display is still a few degrees away from
the correct temperature? For instance, the next
segment starts at 1448 instead of the programmed
temperature of 1450.
What you are describing is normal for a digital control-
ler. There is a delay of several seconds between the actual
kiln temperature and the temperature shown in the con-
troller’s display window.
Since the kiln reached the temperature that you pro-
grammed, the controller began the next segment even
though the display window still showed a lower tempera-
ture. The controller didn’t wait for the temperature in the
display window to catch up with the kiln’s actual tempera-
ture.
On multiple-zone kilns,the temperature display is an av
-
erage of the temperatures from all zones, and the delay be
-
tween the display temperature and the actual temperature
is even longer.
I programmed a FULL rate, yet my kiln heated at only
550 degrees F per hour.
The controller is limited by the heating capacity of each
kiln. So, the maximum rate varies depending on type of
kiln, density of load, etc.
The alarm on my Sentry sounds a minute into each
firing. Why is the alarm going off?
The alarm was set to a temperature below the current
temperature. To deactivate the alarm for your next firing,
set it to 0.
Firing to cone 04 at Fast speed in Cone-Fire mode
takes 7 ½ hours. Is there a way to speed up the firing
for my thin, slip-cast ware?
Afteryou program the firing, usethe SPdoption tomake
thekiln fire faster(page 19). Youcan shortena7 ½ hourfir
-
ing to 5 ½ hours.
To fire even faster, use Ramp-Hold mode to program
faster rates in the cone 04 firing schedule (pages 32 - 33).
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