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 progammable temperature controller


Photo of a GB1 temperature controller.The GB5 is a temperature controller designed for serious artists and craftsmen who need to simultaneously control up to five annealing ovens, burnout ovens, kilns, lehrs, or furnaces.
This fully programmable unit allows a virtually limitless number of temperature profiles while maintaining Digitry’s famous ease of operation. The GB5 can monitor and control any oven for over eleven months, and each temperature profile can include increasing and decreasing ramps as well as soaks.
Best of all, the GB5 is made by Digitry — a respected supplier to the art community since 1981. This newest unit combines the proven accuracy and reliability of its predecessors with the latest advances in digital electronics.
So if you’re ready to experience an exciting new level of productivity in your studio, you’re ready for a GB5.


 Features and Benefits
  • Centralized monitoring and independent control of five ovens, kilns, lehrs or furnaces eliminate the need for separate controllers.
  • Scanning feature displays time and temperature of each oven.
  • Automated control eliminates time-consuming and awkward manual temperature adjustments while achieving smooth ramping.
  • Up to 15 set points per oven gives you a nearly limitless number of temperature profiles with automatic calculation and control of ramps between set points.
  • Simple programming makes it easy to specify over 500 hours per step, allowing a total time of more than 11 months.
  • Stores as many as 4 extra profiles for quick retrieval.
  • Retains all temperature profiles — even without power.
  • Automated control lets you set your own schedule — no need to be on-site for set point changes. Fire your kiln during lower-cost, off-peak energy periods.
  • Delayed start allows automatic preheating so that your oven is ready when you are.
  • Skip-step capability and keypad-initiated soak provide extra control for special techniques such as kiln forming and fusing.
  • Intelligent recovery protects your work from power failures. After an outage, the controller automatically decides how best to proceed.
  • Audio alarms signal thermocouple burn-out.
  • The large LED display clearly indicates unit monitored, program step, remaining step time, temperature, and status.
  • Key lock prevents accidental or unauthorized program changes (optional).
  • Digitry’s unique Power Sharing capability can help in situations where available power is limited (optional).
  • PC connectivity allows you to transfer programs between GB5 and PC as well as log data, graph and remotely monitor programs (optional).
  • Control furnaces with 4–20 mA current loop output for SCRs and motorized valves (optional).
  • Standard features include remote thermocouple amplifiers (sending units) with automatic cold junction compensation, temperature readings in degrees Fahrenheit or Celsius (user selectable).
  • Other system options include any combination of chromel-alumel (Type K) and platinum-rhodium (Type R or Type S) thermocouples, as well as proportional control and remote display repeaters. GB5
How easy is the GB5 to program? This easy...
Press: To:
let the GBl know you want to program profile #5.
put the GB5 into Program Mode.
program the oven to ramp up, evenly to 650°F in
2 hours and 45 minutes. This is set point 1.
tell the oven to soak at 650°F for 3 hours.
This is set point 2.
ramp up to 1675°F in 3 hours.
This is set point 3.


soak at 1675°F for 6 hours.
This is set point 4.
ramp down to 900°F in 9 hours.
This is set point 5.
  The profile is now entered.
B return to Monitor mode.
E5 start the oven running.

Graph of temperature profile just entered above.

Photo of the faceplate of the GB1.

 GB5 Specifications

The GB5 Programmable Temperature Controller requires a sending unit for each oven. Sending units for platinum thermocouples (Type R or S) are different from the standard Type K sending units.

Power Reqirements: 3 watts at 110–120 volts A.C., 60 Hz, grounded
outlet (220–240 volts, 50 Hz available)
Temperature Input for Each Oven: Type K: 32–2400°F (0–1300°C) or
Type S or R: 50–3200°F (10–1700°C)
Automatic cold junction compensation
Resolution: 1 part in 4100
Repeatability: 1 degree
Timing: Crystal controlled timer
Output Choices for Each Oven: • ON/OFF Control for mercury or mechanical contractor; 3 amps at 24–140 volts A.C. (24–280 optional), fused internally or
• 4–20 mA current loop or
• 9 volt DC for solid-state relays
Programming: 9 profiles (5 ovens + 4 additional profiles), each having up to 15 steps of up to 546 hours each, for a total of over 341 days per profile
Dimensions (HxWxD): 9" x 13" x 6" (approx.)
Operator Interface: • 1/2"  7-segment red LEDs
• 16-position dust and moisture-resistant, field replaceable, sealed keypad


 GB5 Notes

Digitry is pleased to announce the availability of two special purpose variants of the GB4. These were developed at the behest of several of our customers.

  1. Zone model

  2. Power Sharing model

These variants are effected purely by means of software. If you think that either of these might be useful to you, it is merely necessary to install a new ``EPROM'' memory chip. You can do this yourself, so you do not have to send in your controller for service.

1. Zone Model  Some large kilns have trouble keeping a uniform temperature throughout. Or sometimes you don't necessarily want uniform heat: for example, in kiln-forming a large piece, where some sections are thicker or have to slump more. Because of these considerations, some kilns are set up with independent banks of heating elements arranged into zones. In such a situation it is natural to use several (or all) channels of a GB4 to control the various zones. Each zone has its own thermocouple and relay for its heating coils. If you want to heat the whole kiln uniformly, you would program the same temperature profile onto each channel and then start them all at the same time. The only sticky wicket in this scheme is the GB4 autohold function. If one zone goes into autohold mode, its timer stops advancing while the other zones timers do not. This causes the zones to get out of synch with each other. Some zones may end up being one or more steps ahead of the others. This is NOT GOOD.

In the past, we have tackled this problem by completely disabling the autohold. We discovered that this was NOT GOOD either. Many customers rely on autohold without even realizing it. (That's because it's automatic!) When it disappeared it was noticed and missed. To resolve this quandary, the new zone variant stops the timers of all the zones whenever any zone goes into autohold mode. This means that the zones will never get out of synch, and you will still have autohold! It is possible to include any number of channels in this zone scheme. For example, you can have channels 1, 2, and 3 linked as zones in one kiln, and have channels 4 and 5 completely independent, as in a normal GB4. [What you can't have is channels 1, 2, and 3 as zones in one oven and channels 4 and 5 as zones in another --- only one zone set per GB4]. The number of channels linked as zones is fixed by the EPROM chip, so please specify how many when ordering this option.

2. Power Sharing Model  Some shops have limited electrical power, or have commercial pricing that charges a great premium if you exceed a certain number of amps at any moment; i.e. this is based on peak usage, not average. (Just as a 100 amp fuse will blow at 120 amps even if your average power draw is only 20 amps, the limitation is based on the maximum, not the average.)

So what do you do if you only have 100 amp service and have two 60 amp kilns and a 30 amp kiln? If you could be sure that both 60 amp kilns would never be heating at the same time, you could still use all three. This is where the Digitry Power Sharing GB4 can help you out. It will never allow more than one kiln to be on at a time. You may say, "But what if I want to bring up both my 60 amp kilns to 900 F at the same time? This won't let me do it!" That is correct --- it won't. You don't have enough power available to do that. But the Power Sharing GB4 will let one kiln heat and then automatically switch over to the other kiln. The GB4 cannot create power (this being against one of the laws of nature) but it can help to manage the power you have. In soaking, or ramping slowly, the "duty cycle" (percentage of time requiring heat) is frequently low enough that each kiln can get the power it needs; we just need a traffic cop to see that only one at a time gets it. The piggies, contrary to their wont, must all line up in single-file to get their turn at the trough. Or, to quote the old nursery rhyme:

One thing at a time, and that done well

Is a very good rule, as many can tell.
 For More Information
If you have a need to control up to five annealing ovens, let us give you the facts on our GB5 Programmable Temperature Controller. You’ll see why Digitry has set an international standard for microprocessor-based temperature controllers.
Please view our web pages at www.digitry.com, where you can find additional information, including product descriptions and manuals, usage tips, price sheets, and order forms.
Address inquiries on Digitry’s GB Series controllers to:
Digitry Company, Inc.
449 Forest Avenue, Suite 9
Portland, ME 04101
Phone: (207) 774-0300
FAX: (617) 484-5220
E-mail: info@digitry.com


Equipment Manuals
Since the beginning of 2002, Digitry's GB1 has been available with a choice of two interfaces: the Classic Interface and the Step-Time Interface. With the Classic Interface, the user enters the total time from the beginning of the profile to the end of each step. With the Step-Time Interface, the user enters the time just for each step itself. Manuals for both interfaces are available below.
GB4 manual 

The above manuals are in Adobe .PDF format. If you need a free copy of the Adobe Acrobat Reader, you may download one at this link.

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