Probe thermometers

In preparation for the screen, a sufficient number of scoring sheets are filled in with the appropriate information. Then the cart employed as a mobile testing station is checked to ensure that all the necessary equipment (empty wire-bottom cage, blunt probe, penlight, 1/2 in. diameter steel rod, force transducer, ink pad, pad of blotting paper, ruler, and electronic probe thermometer) are on the cart and in forking order. Each animal is then evaluated by the following procedures. 

The electronic probe thermometer (with a blunt probe) is used to take a rectal temperature, allowing equilibrium for 30 sec before the reading is recorded. 

Bile secretion is studied in anesthetized bile fistula rats, which are anesthetized by an intraperitoneal injection of pentobarbital sodium (60 mg/kg), tracheotomized, and one jugular vein per rat is cannulated for intravenous administration (bolus injection or infusion of the drug candidate). Anesthesia is maintained for up to 7 hours by subcutaneous infusion of pentobarbital sodium (adjusted to the aesthetic depth of the individual animal about 24 mg/kg/h). Body temperature is monitored with a rectal probe thermometer, and temperature is maintained at 37 °C by means of a heated surgical plate. 

Add the ammonium chloride to the beaker. Stir the chemicals with the temperature probe/ thermometer. Do not move the beaker from the mat. As the temperature falls, the water under the beaker will freeze, sticking the beaker to the mat. The temperature may go well below -10°C. 

Probe Thermometers. Volume expansion thermometers use the expansion of liquids with rising temperature through a narrow tube. The expansion coefficient, defined as the increase in volume per unit volume per unit rise in temperature, is 0.00018 per Kelvin for mercury and 0.00109 per Kelvin for ethyl alcohol colored with dye. Calculating temperature from the actual random thermal motion velocity of every molecule, or the energy contained in a vibrational excitation of every molecule, is impractical. So temperature is measured indirectly in most applications. Different metals expand to different extents when their temperature rises. This difference is used to measure the bending of two strips of metal attached to one another in outdoor thermometers. Thermocouples use the Seebeck or thermoelectric effect discovered by Cerman physicist Thomas Johann Seebeck, in which a voltage difference is produced between two junctions between wires of... 

If no fixed temperature measuring point is incorporated in the mould, it is possible to use probe thermometers as an aid. To carry out any measurements in the cavity, involves interrupting the cycle. The negative effects, which then arise on the accuracy of measurement and the production cycle must not be left out of consideration. But in no case should the measurement of the mould temperature - at least at one specific comparison point or reference point - be neglected. 

Instruments based on the contact principle can further be divided into two classes mechanical thermometers and electrical thermometers. Mechanical thermometers are based on the thermal expansion of a gas, a liquid, or a solid material. They are simple, robust, and do not normally require power to operate. Electrical resistance thermometers utilize the connection between the electrical resistance and the sensor temperature. Thermocouples are based on the phenomenon, where a temperature-dependent voltage is created in a circuit of two different metals. Semiconductor thermometers have a diode or transistor probe, or a more advanced integrated circuit, where the voltage of the semiconductor junctions is temperature dependent. All electrical meters are easy to incorporate with modern data acquisition systems. A summary of contact thermometer properties is shown in Table 12.3. 

Resistance thermometers are made of a pure metal, such as platinum, nickel, or copper. The electrical resistance of such a material is almost linearly dependent on temperature. Resistance thermometers are stable, having a small drift. A widely used and the best-known resistance probe is the IW-100 probe, which is platinum, having a resistance of 100 ohms at the temperature of 0 °C. Other resistance values for PT probes are available. The resistance versus temperature values as well as tolerances for platinum probes are standardized. The shape and size of a resistance probe can vary considerably, resulting in changes in probe dynamics. 

The so-called standard instrument is used for interpolation between the fixed points and for the calibration of other thermometers lower in the metrological hierarchy. The standard instrument in the moderate temperature range is a special platinum resistance probe, as it has to fulfill set requirements. It is important in all calibration that traceability to a primary normal, here the fixed-point ITS-90 scale, exists. 

The Nernst equation shows that the glass electrode potential for a given pH value will be dependent upon the temperature of the solution. A pH meter, therefore, includes a biasing control so that the scale of the meter can be adjusted to correspond to the temperature of the solution under test. This may take the form of a manual control, calibrated in 0 C, and which is set to the temperature of the solution as determined with an ordinary mercury thermometer. In some instruments, arrangements are made for automatic temperature compensation by inserting a temperature probe (a resistance thermometer) into the solution, and the output from this is fed into the pH meter circuit. 

Remove the electrode assembly (and the thermometer probe if used), rinse in distilled water, and place into a small beaker containing a little of the second buffer solution. If the meter reading does not agree exactly with the known pH, adjust the Slope control until the required reading is obtained. 

Check whether the instrument supplied is equipped for automatic temperature compensation, and, if so, that the temperature probe (resistance thermometer) is available. If it is not so equipped, then the temperature of the solutions to be used must be measured, and the appropriate setting made on the manual temperature control of the instrument. 

An Omega model HH22 type J-K digital thermometer, connected to a type K thermocouple probe inserted directly into the flask, was used to measure the temperature. 

A number of variations of the transient hot-wire method have been devised, and an optical method to detect the temperature rise has been used. A modified transient hot-wire technique using a mercury-incapillary probe was introduced by Nagashima et al., in which a thin mercury thread was used as a heater-thermometer and the capillary wall as an insulator. Using this method, they measured the thermal conductivity in mixture systems such as (Na, K)N03, (Li, Na)N03, and HTS(KN03-NaN03-NaN02, 44-7-49 mol.%). ... 

P 60] The dehydration of 1-hexanol to hexane and of ethanol to ethane were conducted at 155 °C. Heating was accomplished by a heating wire inserted in the micro reactor s top plate. This wire was connected to a potentiostat (0-270 V) temperature was monitored by a digital thermometer with the probe close to the reaction channel. A syringe pump was applied for liquid transport [19]. A flow rate of 3 pi min was applied. The alcohols were purged with nitrogen directly prior to reaction to minimize coke formation. 

The pH (or pI) term of the Nemst equation contains the electrode slope factor as a linear temperature relationship. This means that a pH determination requires the instantaneous input, either manual or automatic, of the prevailing temperature value into the potentiometer. In the manual procedure the temperature compensation knob is previously set on the actual value. In the automatic procedure the adjustment is permanently achieved in direct connection with a temperature probe immersed in the solution close to the indicator electrode the probe usually consists of a Pt or Ni resistance thermometer or a thermistor normally based on an NTC resistor. An interesting development in 1980 was the Orion Model 611 pH meter, in which the pH electrode itself is used to sense the solution temperature (see below). 

To do this, the software must be aware of conditions within the reactor therefore, we shall arrange that it is fed with regular messages from a digital thermometer in contact with the fermenting medium. The thermometer, and any other probes in the vessel, send messages to the software in the form of binary strings, such as ... 

Let us assume that messages from the digital thermometer are tagged with the identifier "00." The rest of the message conveys information about the current temperature, T. Table 9.1 shows how the message sent from the digital probe provides information about reactor conditions. 

A Fluke 51 K/J digital thermometer with temperature probe is used to monitor internal reaction temperature. 

A particularly difficult problem in microwave processing is the correct measurement of the reaction temperature during the irradiation phase. Classical temperature sensors (thermometers, thermocouples) will fail since they will couple with the electromagnetic field. Temperature measurement can be achieved either by means of an immersed temperature probe (fiber-optic or gas-balloon thermometer) or on the outer surface of the reaction vessels by means of a remote IR sensor. Due to the volumetric character of microwave heating, the surface temperature of the reaction vessel will not always reflect the actual temperature inside the vessel [7]. 

Temperature measurement is achieved by means of a remote IR sensor beneath the lower outer surface of the vessels. The operation limit of the IR sensor is 400 °C, but it is regulated by the software safety features to 280 °C as the operation limits of the materials used are around 300 °C. For additional control, temperature measurement in a reference vessel by means of an immersed gas-balloon thermometer is available. The operational limit of this temperature probe is 310 °C, making it suitable for reactions under extreme temperature and pressure conditions. 

The simplest experimental arrangement (two-probe method) uses two thermometers one on the thermal bath at Ts, the second on the warm end of the sample together with the heater (see Fig. 11.1). Such configuration can be used when one is sure that contact resistances are negligible compared with the sample thermal resistance. This is seldom the case at very low temperature. A sample bath (and sample support) temperature drop ... 

COVER ELECTRONIC THERMOMETER PROBE PLASTIC DISPOSABLE 100S 6515013738659 PG 9.35 ... 

Temperature Recording. Use an accurate temperature-sensing device, such as a clinical thermometer or thermistor or similar probe, that has been calibrated to ensure an accuracy of 0.1° and has been tested to determine that a maximum reading is reached in less than 5 min. Insert the temperature-sensing probe into the rectum of the test rabbit to a depth of not less than 7.5 cm and, after a period of time not less than that previously determined as sufficient, record the rabbit s temperature. 

Figure 2 gives a schematic of the apparatus used for pH measurements at 25 and 80°C. It consisted of a stoppered Erlen-meyer flask submerged in a temperature bath regulated at either 25 or 80°C. The contents of the flask were stirred by means of a magnetic stirrer coupled to a motor beneath the bath. A pH probe and thermometer were inserted through the stopper at the top of the flask and another hole was stoppered for use in pi-peting solution into or out of the flask. 

Figure 11.15. Schematics of the optical arrangement and temperature probes for the Cr+ fluorescence lifetime-based fiber optic thermometers. F = short-pass optical filter Fa = bandpass or long-pass optical filter LD = laser diode LED = light emitting diode S = the fluorescence material used as sensing element vm = signal to modulate the output intensity of the excitation light source v/= the detected fluorescence response from the sensing element.

The subsequent development of laser diode sources at low cost, and improved electronic detection, coupled with new probe fabrication techniques have now opened up this field to higher-temperature measurement. This has resulted in an alexandrite fluorescence lifetime based fiber optic thermometer system,(38) with a visible laser diode as the excitation source which has achieved a measurement repeatability of l°C over the region from room temperature to 700°C, using the lifetime measurement technique. 

K. T. V. Grattan, A. W. Palmer, and Z. Zhang, Development of a high-temperature fiber-optic thermometer probe using fluorescent decay, Rev. Sci. Instrum. 62(5), 1210-1213. 

To test for temperature accuracy of a column oven, one should place the temperature probe/sensor of a calibrated/verified electronic thermometer (with at least 0.5°C precision) into the oven. The probe/sensor should not make contact with anything inside the oven. With the oven door closed, allow the temperature to stabilize for at least 20 min at each tested temperature (e.g., 30, 45 and 60°C). The thermometer s temperature should then be recorded at each temperature. The difference between the actual and set temperature should typically be within 1°C. 

Fig. 3.27. The Pask-Plesch reaction calorimeter, approximately to scale. A phials of reagents, B phial magazine, C cold finger (not essential), D phial breaker, E vessel of calorimeter, F heater, Gj Pt wires of the conductivity probe, Gj terminals, H vacuum jacket, thermometer probe, terminals from thermometer probe and the compensating leads, K tap for evacuation of pseudo-Dewar space or admitting air, M magnetic pusher, T main tube,...

---