Physiological - Biological Temperature Controller TMP-5b

Optimized for seriously shielded environments in microelectrode laboratories. Its output current is as smooth as the current of a lead battery (with the 12 V FINE DC power driver stage). This design fulfils all requirements of any sophisticated electrophysiology application, even in close proximity to any, high impedance recording electrode. The best references of the noise free performance are the patch clamp setups with GigaOhm impedance electrodes next to the heating elements.

General Description

The Physiological - Biological Temperature Controller is an intelligent PID controller, based on an internal microcontroller. Typical PID controllers modulate the effective value of the output voltage by PWM. In our equipment the PID characteristics were realized by slow PWM modulation through exponential output voltage changes. We implemented a learning algorithm into the firmware to introduce adaptive PID parameters. The reason, why we made such huge efforts instead of the simple way was to provide fully noise free heating. Furthermore we have built sophisticated fault diagnostic features into the firmware. These unique fault diagnostic algorithms have been developed specifically for biological heating applications. For the details please see the User Manual.

        Click on the picture to get it in full size

We have developed a universal Physiological - Biological Temperature Controller construction that can be manufactured with three different power driver stages, depending on the power requirement of the thermal process under control. Certainly, only one power driver stage can be installed in a Physiological - Biological Temperature Controller. The price of the Temperature Controller does not depend on the kind of the power driver stage installed in it. The appropriate power driver stage for the actual heating application should be chosen before placing an order (our design engineers are open for discussion).

Choice of the Power Driver Stages

    • 12 V FINE DC: max. 36W. It is optimized for microelectrode laboratories, for seriously shielded environments.

        Its output current is as smooth as the current of a lead battery. This power driver stage fulfils all special requirements

        of any sophisticated electrophysiology application, even in close proximity to any, high impedance recording electrode,

        like in a patch clamp setup.

    • 24 V pulsing DC: max. 75 W. Extra Low Voltage, electrically secure heating for general purpose.

    • 115/230 VAC Huge-power: up to 3.5 kW. It is optimal to control the temperature of large heated objects.

Specifications / Technical Data

The controlled temperature range: 0 Centigrade to 70 Centigrade, in 1 Centigrade steps

The available temperature range in a given application does not depend on the Physiological - Biological Temperature Controller, but on the heater device itself. Either the temperature sensor or the Physiological - Biological Temperature Controller have a full scale value of 120 Centigrade. In most cases the real allowed temperature limit is much less than 120 Centigrade. Higher temperatures can be reached with specially designed, larger power heating devices. If you require higher temperature than 50 Centigrade, please consult our development engineers in advance.

Resolution of the temperature measurement: 0.1 Centigrade

Hysteresis (approximately): 0.3 - 0.5 Centigrade. The actual hysteresis depends on the thermal capacity and the heat drain appearing on the heated object.

In our terminology, the expression "internal sensor" means that the temperature sensor is built into the heated object. In every heated object manufactured by Supertech Instruments there is a built-in internal temperature sensor.

Both internal and external temperature sensors can be connected to the Physiological - Biological Temperature Controller. The internal/external sensor selector switch is located at the back side of the Physiological - Biological Temperature Controller.

Display: 4 x 16 characters alphanumeric LCD with bright blue backlight

Programming: three pushbuttons on the front, in menu system

Automatic internal diagnostic and fault protection algorithms in the software

Flash program memory

Non-volatile EEPROM memory to store parameters used the previous time

Temperature sensor (either in internal or external arrangement): DS18S20 from the successor of Dallas Semiconductor

Dimensions of the instrument: 290 x 250 x 90 mm

Mains voltage: 100-120V or 220-230V (chosen by an internal selector switch, fixed in the factory)

Power consumption of the Physiological - Biological Temperature Controller itself: 80 VA. The output power consumed by the heated object is additional.

Weight: 2.8 kg

The complete User Manual of the Physiological - Biological Temperature Controller is available for download.

Small Animal Heating Pads

We offer a range of small animal heating pads. The appropriate size for the actual application can be chosen beforehand (depending on the size of your species).

Our animal heating pads can be used up to 50 Centigrade.

All heating pads are equipped with internal temperature sensors. It is recommended to use them instead of external temperature sensors. See the explanation below in the "Special Considerations about the External Temperature Sensors" section.

Small animal heating pads can be cleaned with damp cloths, using non-aggressive solutions. They can be used in humid environments, but it is prohibited to immerse them into water or use them under water!

On the side of every heating pad there is a M4 screw. This screw is the ground connection point. Electrically the metal enclosure of the heating pad is isolated from the internal circuitry. For the sake of perfect noise suppression you should connect the heating pad via the M4 screw to the central ground point of the electrophysiology rig.

Standard Sized Stainless Steel Heating Pads

Our range of standard size heating pads:

    • 115 x 80 mm, 12W, (for mouse, AHP-1)

    • 170 x 115 mm, 24W, (for rat, AHP-2)

    • 330 x 145 mm, 36W, (for cat or rabbit, AHP-3)

            Click on the picture to get it in full size

The temperature variation between any two points of the heating pads is not more than 1 Centigrade (in worst case).

Standard size heating pads are covered by stainless steel. This provides great rigidity and mechanical protection. Standard heating pads are 12 mm in thickness, with 2 mm added for the rubber feet.

Heating pads employ a Physiological - Biological Temperature Controller fitted with 12V FINE DC or 24V DC power driver stage (depending on the size). Standard size heating pads work on 12V FINE DC.

Custom Size Heating Pads

Custom size heating pads can be ordered for special applications. The thickness of the custom size heating pads vary between 12 mm and 20 mm, depending on the actual size. Custom size heating pads are multilayer constructions. The top layer is a thin stainless steel plate, followed by a thick aluminum plate. The third (bottom) layer is a heat-insulating plastic plate. The thickness of the aluminum plate (middle layer) can not be decreased too much because it contains electronic circuits. There are active electronic heat generators used as heating elements in the heating pads. The heat generators are realized by electronic circuits (transistors, diodes and resistors). The heating pads are covered by stainless steel by default. Anodized aluminum top is available upon request.

Special Considerations about the External Temperature Sensors

An external temperature sensor (DS18S20 from successor of Dallas Semiconductor) can be connected to the Physiological - Biological Temperature Controller. A tailored sensor with 1.5 meter BNC cable is available in our product choice. The actually used sensor can be selected with a toggle switch on the back side of the temperature controller. However, we DO NOT RECOMMEND using an external temperature sensor. Eliminating an external temperature sensor is possible because there is a built-in internal temperature sensor in every heated object manufactured by Supertech Instruments. Please DO NOT use an external sensor, except under particular circumstances. The reasons are below, why we suggest this.

1) Using an external temperature sensor, the average temperature of the heated object will be accurately the same as it has been set on the Physiological - Biological Temperature Controller, but a hysteresis (fluctuation in temperature) will appear. The reason of the appearance of the hysteresis is explained in the next paragraph. Using an internal temperature sensor built into the heating pad, the average temperature of the heated object will surely be a little bit less than the setup temperature of the Physiological - Biological Temperature Controller, but the hysteresis will be negligible. Occasional calibration of the temperature of the heated object (animal) may be necessary. The calibration process is uncomfortable, but eliminating the hysteresis is essential, because the target is a living animal or biological tissue. The change of temperature has a stimulating effect on the biological object, which may disturb or modulate the experiment.

2) Heating tasks in biology bring up special difficulties. The heat capacity and the thermal time constant of the heated object are huge because the object is usually an animal or living tissue. The thermal resistance between the external temperature sensor and the heated object is significant (in simple words, there is a bad thermal connection). This is true either for a technically realized heated object or for a heating pad - animal combination. This can result a significant hysteresis (5-6 Centigrade in exceptionally bad cases) when using an external sensor. This big hysteresis appears in our competitor's products, too. It has been measured in different labs under different circumstances, but neither hardware nor software based solution could be found to eliminate this effect. As a good solution, we developed a predictive, learning algorithm for the Physiological - Biological Temperature Controller with a software module running in the built-in microcontroller. This algorithm uses the device's internal temperature sensor. This way a stable, fine regulation of the temperature can be achieved.

3) Most cases the heated object is an animal. The animal is not an "iron cube". It has its internal temperature regulation that may interfere with the predictive algorithm running in the microcontroller of the Physiological - Biological Temperature Controller. The natural temperature regulation process in the animal is not synchronized to the software-based control process. That is, why the animal itself can not be included in the intelligent predictive algorithm.

4) DS18S20 is one of the most sophisticated temperature sensors available. It communicates with the host microcontroller in a fully digital way on a 1-wire bus, on standard TTL voltage level. Although it is a professional sensor, the TTL voltage level is much higher than the amplitude of the usual electrophysiological signals. As a result it generates digital noise, so it should not be placed in a highly sensitive shielded environment or in a tissue bath close to the working biological target.

5) Using the internal temperature sensor (built in the heating pad) makes it easier to prepare the tissue or the animal. It is not necessary to keep the rectal or tissue bath sensor always clean and sterile.

6) It is not necessary to buy an external temperature sensor.

If you decide to use the internal (built into the Heating Pad) temperature sensor, you can monitor the core temperature of the target animal exactly by using a Biological Temperature Meter manufactured by Supertech Instruments. You can see the description of this equipment on the Temperature Management in Physiology and Biology page.

Temperature Sensors

• DS18S20 temperature sensor: compatible with the Physiological - Biological Temperature Controller TMP-5x

    Main features:

    - Diameter: 4.5 mm, it can be used as rectal sensor for larger animals (and maybe rats)

    - Digital, with excellent long term stability

    - Factory calibrated, with better than 0.1 Centigrade accuracy

    - Relatively strong and durable

    - Unshielded, it should not be used close to high impedance recording electrodes

• Pt100 temperature sensors: compatible with the Precision Biological Temperature Meter BTM-xx

    You can see their description on the Temperature Management in Physiology and Biology page.

For using a tunnel heater and a heating pad together, only one Physiological - Biological Temperature Controller is needed, assembled with a 24V DC power driver stage. The tunnel heater and the heating pad are connected electrically, so they are heated up and controlled by the same temperature controller.