Temperature Management in Physiology and in Biology

 

 

Physiological - Biological Temperature Controller  TMP-5b

 

The most important feature of the Physiological - Biological Temperature Controller TMP-5b, that it is optimized for microelectrode laboratories, for seriously shielded environments. Its output current is as smooth as the current of a lead battery (with the 12 V FINE DC end-stage, see below). This design fulfils all the special requirements of any sophisticated electrophysiology applications, even in close position to any, high impedance recording electrodes. Good references are the patch clamp setups with GigaOhm electrodes next to the heating elements.

 

General Description:

 

We have developed one universal Physiological - Biological Temperature Controller construction, but it can be built with three different power end-stages, depending on the power requirement of the thermal process under the control. Naturally, only one power end-stage can be installed in a Physiological - Biological Temperature Controller. The price of the Controller does not depend on the kind of the power end-stage installed in it. You should choose the appropriate power end-stage according to the requirements of your actual heating application before placing an order.

 

        Click on the picture to get it in full size

 

The Physiological - Biological Temperature Controller is based on an internal microprocessor. The microprocessor on the front plate talks with the user in an intelligent menu system. The firmware in the built-in microprocessor of the Physiological - Biological Temperature Controller realizes a semi-switching control algorithm with several special fault diagnostic features. These unique fault diagnostic algorithms have been developed especially for the biological heating applications. For the details please see the User Manual.

 

The choice of the power end-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 end-stage fulfils all the special requirements

        of any sophisticated electrophysiology applications, even in close position to any, high impedance recording electrodes,

        such as patch clamp setups.

 

    - 24 V pulsing DC: max. 75 W. It is a low voltage, electrically secure version for general purposes.

 

    - 115/230 VAC Huge-power version: up to several kW. It is optimal to control the temperature of great heated objects.

 

Technical data:

 

The controlled temperature range: 0 Centigrade to 120 Centigrade, in 1 Centigrade steps

 

The available temperature range in a given application depends not on the Physiological - Biological Temperature Controller, but on the heating device itself. In most of the cases the real temperature limit is less than 120 Centigrade. Higher temperatures can be reached with specially designed, bigger power heating devices. If you require higher temperature than 50 Centigrade, please consult our engineers in advance.

 

The resolution of the measurement: 0.1 Centigrade

 

Histheresis (approximately): 0.3 - 0.5 Centigrade. The actual histheresis depens on the thermal capacity, and the heat drain appearing on the heated object.

 

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.

 

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

 

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 the parameters used last time

 

Temperature sensor (either in internal or external arrangement): DS18S20 from 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 without output load, the Physiological - Biological Temperature Controller only: 80 VA

 

Weight: 2.8 kg

 

Special considerations about external temperature sensors:

 

An external temperature sensor (DS18S20 from Dallas Semiconductor) can be connected to the Physiological - Biological Temperature Controller. There is such a tailored sensor in plastic enclosure, with 1.5 meter BNC cable in our standard product choice. On the back side of the Physiological - Biological Temperature Controller the actually used sensor can be selected with a toggle switch. However we do NOT RECOMMEND to use any external temperature sensor. It is possible to eliminate the usage of the external temperature sensor, because in every heated object manufactured by Supertech Instruments there is a built-in internal temperature sensor. Please, do NOT use an external sensor, except under particular circumstances. There are a few reasons, why an external sensor should not be used in most of the applications:

 

1) Using an external temperature sensor, the average (middle) temperature of the heated object will be accurately the same as it has been set in the Physiological - Biological Temperature Controller as setup temperature, but a histheresis (oscillation of the temperature) will appear. The reasons of the generation of the histheresis is explained in the following paragraph. Using an internal temperature sensor built into the heating pad, the average temperature of the heated object will be surely less than the setup temperature set in the Physiological - Biological Temperature Controller, but the histheresis will be negligible. Using an internal temperature sensor, sometimes a calibration will be necessary with a usual heated object. The calibration process is uncomfortable, but eliminating of the histheresis is essential, because the target is a living biological animal or tissue. For biological objects the change of temperature acts as a stimulating effect, what may disturb or modulate the experiment.

 

2) There are special difficulties appear in heating tasks in biology. The heat capacity, and the thermal time constant of the heated objects are huge, because the object is usually an animal or a living tissue. The thermal resistance of the external temperature sensor to the heated object is quite big (in simple words usually there is a bad thermal connection). These statements are true for the technically realized heated objects (as our products), and for the Heating Pad - animal combinations, as well. These effects together result big histheresis (6-8 Centigrade) if you try to use an external sensor. We tested it in many labs, under very different circumstances, but we could not find any hardware and/or software trick to eliminate this effect. As a good solution, we developed a predictive, learning algorithm for the Physiological - Biological Temperature Controller what software runs in the built-in microcontroller. This algorithm uses the internal temperature sensor, what is built into the heated object. This method results a stable, fine regulation of temperature.

 

3) The heated object in most of the labs is an animal. The animal is not an "iron cube", it has got a "built-in" biological temperature control system. If the temperature regulation system works in the animal, it disturbs the predictive algorithm running in the microcontroller of the Physiological - Biological Temperature Controller, because the regulation process in the animal is not synchronized to the software-based control process.

 

4) DS18S20 is one of the most sophisticated temperature sensors in the choice of the semiconductor manufacturers. This is a real top model. 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 bigger than the amplitude of the usual biological 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) It is easier to prepare the tissue, or the animal. It is easier to arrange the tissue bath. It is not necessary to keep the rectal, or the bath sensor always clean and sterile.

 

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

 

However if you would like to monitor the core temperature of your animal exactly, please use a Biological Temperature Meter (see its description below).

 

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

 

 

Small Animal Heating Pads

 

In our choice there are Small Animal Heating Pads. You shold choose the appropriate size for your actual application (depending on the size of your species).

 

Small Animal Heating Pads can be used up to 50 Centigrade.

 

In all the heating pads there are internal temperature sensors. It is recommended to use them. See the explanation above at the Physiological - Biological Temperature Controller.

 

The actual choice of the standard size Stainless Steel Heating Pads:

    - 115 x 80 mm, 12W, (for mouse)

    - 170 x 115 mm, 24W, (for rat)

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

 

The temperature difference on the top of the Small Animal Heating Pads, between any two points, is not more than 1 Centigrade, in worst case.

 

The Small Animal Heating Pads can be washed with wet clothes, with non-agressive solutions. They can be used in humid environment. But it is prohibited to immerse them in water, or try to use them under water!

 

To use the Small Animal Heating Pads you should buy a Physiological - Biological Temperature Controller, assembled with 12V FINE DC, or 24V DC (depending on the size of the Heating Pad) power end-stage. The standard size of heating pads work on 12V FINE DC.

 

Stainless Steel Heating Pads:

 

            Click on the picture to get it in full size

 

The top of these versions of Small Animal Heating Pads are covered with stainless steel plates. It gives a great rigidity, and the opportunity for shielding. On the stainless steel cover there is a metric M4 screw to connect the plate to the central ground point of the lab for shielding purpose. The thickness of the standard heating pads is 12 mm, plus 2 mm the height of the legs.

 

Custom Size Heating Pads:

 

Custom size heating pads can be ordered for special applications, as well. The thickness of the custom size heating pads is 12 mm to 20 mm. The thickness depends on the actual measures. The custom size heating pads are multilayer constructions. The top layer is a thin stainless steel plate. Below the stainless steel top plate there is a thick aluminium plate. The third (bottom) layer is a heat insulator plastic plate. The thickness of the aluminium plate (middle layer) can not be decreased too much, because there are electronic circuits inside the aluminium plate. In the heating plates there are active electronic current generators. They are used as heating elements. The current generators are realized by electronic circuits (transistors, diodes, and resistors). The heating pads are manufactured of stainless steel top by default, but if you need it, your heating pad can be realized with anodized black aluminium top.

 

 

Precision Biological Temperature Meter  BTM-3a

 

The Biological Temperature Meter is a high accuracy temperature measuring equipment optimized for the temperature range of the living tissues. The resolution of the measurement is 0.1 Centigrade, and the accuracy of the Biological Temperature Meter can be trimmed as good as your temperature reference used for calibration.

 

            Click on the picture to get it in full size

 

There is an important accessory of Biological Temperature Meter, what always must be used. It is called Pt100 Transducer Box. It is a small equipment in a plastic enclosure. Pt100 Transducer Box should be positioned very close to the Pt100 sensor. The wires of the Pt100 sensor must be minimized as short as possible to keep the level of electric noise (disturbing the temperature measurement) on a low level. The Biological Temperature Meter, and the Pt100 Transducer Box are connected together with a 1.6 meter long wire, wich is not sensitive to disturbing electromagnetic fields. The Pt100 Transducer Box is designed to accept any kind of Pt100 sensors. This feature gives you the possibility to choose that sensor, which optimally fits your experimental environment. The only limitation is, that your sensor must be Pt100 type, but the size, shape, and enclosure of the sensor can be chosen freely.

 

    Click on the picture to get it in full size

 

There are two internal potmeters located inside the Pt100 Transducer Box. Their names are Gain, and Shift. With these potmeters the error of the temperature measurement can be trimmed to absolute zero. It is always necessary to adjust these potmeters after changing the sensor, because the commercial sensors have got quite high tolerances, and this tolerance can be trimmed to zero. The accuracy of your measurement depends only the correctness of your temperature references what you use to calibrate the Pt100 Transducer Box. The price of the Pt100 Transducer Box is included in the price of the Biological Temperature Meter.

 

Technical data:

 

The measured temperature range: - 40 Centigrade to 120 Centigrade

 

The resolution of the measurement: 0.1 Centigrade

 

Display: 3.5 characters numeric LCD with backlight

 

Analog voltage output for PC-based DAQ systems: 0.1 V, or 0.01 V per Centigrade (jumper selectable)

 

Temperature sensor: Pt100 (the equipment is compatible with any commercially available Pt100 sensors)

 

Dimensions of the Biological Temperature Meter: 200 x 160 x 75 mm

 

Dimensions of the Pt100 Transducer Box: 90 x 50 x 25 mm

 

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

 

Power consumption: 30 VA

 

Weight: 1.8 kg

 

 

Heater for Microscope Stage

 

The Heater for Microscope Stage is a custom-designed product. We design a special heater pad for you. We design it together with you, according to your special aspects, and requirements. The price is fixed in advance as a unit-price, because the different versions are similar to each other both in their material, and labour costs. In this way we can focus on the professional aspects during the design process, not on the expenses.

 

Usually the Heaters for Microscope Stages are black, hard-anodized aluminium plates, with 10, or 12 mm in thickness. Sometimes they are dull (unglazed) aluminium products. The aluminium gives a great durability, and rigidity. On the Heaters for Microscope Stages there are usually great holes covered with a thick glass plate, or without glass, depending on the actual requirements.

 

In the discussion phase we could provide you a schematic design proposal if you would send us a drawing of your stage, plate, and other environmental parts.

 

An example:

 

                Click on the picture to get it in full size

 

In the picture you can see a square-shaped example. This model is covered with a thick glass plate. This style of heater must not be used on an inverted microscope.

 

Other style of heaters could be either round-shaped equipments, as well. The outer diameter, the aperture, the nest of the chamber (if necessary), and the height of the focus plane could be specified by you. The only limitation is, that we have to take care to provide enough space for the heater current sources. We use active electronic current generators as heating elements. The heater current generators are located around the hole on the top, or bottom side of the heater plate.

 

The temperature difference on the top of the Heater for Microscope Stage, between any two points, is not more than 1 Centigrade, in worst case.

 

In the Heaters for Microscope Stages there are internal temperature sensors. It is recommended to use them. See the explanation above at the Physiological - Biological Temperature Controller.

 

To use a Heater for Microscope Stage you should buy a Physiological - Biological Temperature Controller, assembled with 12V FINE DC, or 24V DC power end-stage, depending on the actual design..

 

 

Warm Air Jet Heater System for Incubator, Objective or Sample

 

We have been working on the development of a brand new heating method. It is Warm Air Jet Heater System for Incubator, Objective or Sample. We have got several working prototypes in good laboratories under tests. These prototypes are close to the manufacturing phase. The Warm Air Jet Heater System for Incubator, Objective or Sample will be published soon as a new product. In the meantime, if you are interested in the preliminary technical information, please email us. You can see the price details in the Price List.