Digital and PID Temperature Controllers in the 120 °c to 150 °c band. Process and platen heating, adhesive curing, epoxy-encapsulated plates at their limit. Silicone and polyimide are comfortable here; the encapsulant, not the element, is usually what constrains the design. The construction is rated 400 °C continuous, so this band sits inside its ceiling — and where a band sits relative to the ceiling is the whole of the selection argument.
What the 120 °C to 150 °C Band Requires
Process and platen heating, adhesive curing, epoxy-encapsulated plates at their limit. Silicone and polyimide are comfortable here; the encapsulant, not the element, is usually what constrains the design.
| Band | 120 °C to 150 °C |
|---|---|
| This construction, continuous | 400 °C |
The band sits comfortably inside the 400 °C ceiling, which is where a heater should be specified: the margin between the working temperature and the insulation limit is what absorbs a poor thermal path, a warm ambient and a control overshoot without shortening the life of the part.
Why the Boundary Is Where It Is
150 °C is the ceiling of filled epoxy, and on an encapsulated plate the encapsulant fails before either the element or the plate is troubled. It is also roughly where acrylic pressure-sensitive adhesives give up, which matters on any heater that is held on by its own adhesive rather than clamped.
Silicone and polyimide are comfortable through this band with 50 °C of margin in hand; the constraint is usually the bonding system, not the heater.
What a Digital and PID Temperature Controllers Is
Panel controllers to close the loop around the heater: on/off for simple holding, PID where the set point has to be reached without overshoot.
The instrument that closes the loop: it reads a sensor, compares it with a set point and switches the heater. It is what gives a heating system an accuracy figure — no heater has one on its own.
The heat leaves through whatever the component is clamped or bonded to; a sensing component adds no heat of its own and simply has to be in thermal contact with the thing it is reporting on.
| Total thickness | Component |
|---|---|
| Maximum size, one piece | Component |
| Continuous working temperature | 400 °C |
The continuous limit of 400 °C is set by the insulation system. The element alloy would run far hotter; it is never the element that decides.
Which Temperature Is Being Held
Three temperatures matter and they are not the same number: the element temperature, the temperature of the surface being heated, and the ambient. A heater rated for a continuous working temperature is rated at the element — the hottest point in the assembly, and the one nothing on the outside is measuring.
The gap between element and surface is the thermal path. Bonded to metal it may be a few degrees; across an air gap, a void in the adhesive or a dry clamped joint it can be tens of degrees, and every one of them appears at the element rather than at the load.
Attachment and Thermal Contact
A sensing component is fitted where it will read the temperature that matters: against the element for a limit device, against the load for a control device. The two positions give different numbers, and choosing the wrong one is the commonest reason a correctly built loop holds the wrong temperature.
A sensor reads its own junction, not the surface it is near. Bed it in thermal compound, clamp it, or pot it into the assembly: an air gap of a tenth of a millimetre between a thermistor and the plate it is supposed to be measuring is worth several degrees of error, and it is an error the controller cannot see.
Control and Protection
This heater has no way of limiting its own temperature. Resistance heating draws roughly the same power whatever the temperature, so with the load removed, the fluid gone, the fan stopped or the sensor open circuit, the element keeps producing watts until something stops it.
The design must therefore contain a control device and, separately, a protective one: a controller with a sensor to hold the set point, and a bimetal thermostat or a one-shot thermal cutoff wired in series with the element to open the circuit if the loop ever fails. The two are not interchangeable — a controller that has lost its sensor cannot protect anything, which is exactly the fault the cutoff exists for.
Where This Construction Is the Wrong Answer
- Do not plan on running above 400 °C. That ceiling belongs to the insulation system, not to the element alloy, and it is not a figure that derating extends — past it the insulation degrades and the dielectric strength goes with it.
- Do not rate this component as though it were the heater. It carries a contact rating or a tolerance class; the heater next to it decides the power, the watt density and the temperature the assembly reaches.
Other Constructions That Hold 120 °C to 150 °C
Constructions in this catalogue that will hold 120 °c to 150 °c continuously:
How to Specify One
This is a made-to-drawing part, so there is no catalogue number to quote. A quotation is built from the following, and the more of it that arrives with the enquiry the fewer rounds it takes:
- The temperature to be sensed or switched, and the tolerance the application actually needs.
- Where the component sits — against the element, in the potting, on the load, or in the airflow.
- The electrical duty: for a switching device, the voltage, the current and whether the load is AC or DC.
- Lead length, insulation and termination, and whether the component is fitted by us into a heater assembly or supplied loose.
- The standard the end product is certified to, so the component chosen is one that fits inside that approval.
Lead time: Samples 7-10 days from approved drawing; production 15-20 days.
Digital and PID Temperature Controllers — Capability Table
These are process limits for the construction, not the specification of one stocked item. Every line is what the factory can hold; what your part holds is fixed on your drawing.
| Parameter | Specification | Limit / note |
|---|---|---|
| Control modes | On/off, PID with autotune, ramp/soak programmes | On/off is adequate for a lagged mass and hopeless for a thin plate |
| Input | PT100, PT1000, NTC, thermocouple type K/J/T/E | Configurable at the front panel |
| Control accuracy | u00b10.1% of span, u00b11 digit | Of the instrument u2014 the loop is only as good as the sensor placement |
| Output | Relay 3 A, SSR drive 12 V DC, 4-20 mA | SSR drive for anything cycling faster than once a minute |
| Alarms | High, low, deviation, sensor break | Sensor break must fail the heater off, and this should be verified rather than assumed |
| Supply | 100-240 V AC or 24 V DC | |
| Panel size | 48x48, 72x72, 96x96 mm DIN | |
| Standard | IEC 60730 / IEC 61010 | Controller safety and functional standards |
Figures are the published tolerance and rating bands of the standard sensor and control components fitted to these heaters. Sensor tolerance classes follow IEC 60751 for RTDs and IEC 60584 for thermocouples; thermostat and thermal cutoff ratings are the component manufacturers' own.
