Testing and calibration equipment for all kind of meteorological sensors
This thermometer calibrating unit is designed for calibrating up to 19 mercury thermometers simultaneously over a wide temperature range.
The major components of this equipment are the temperature bath – including the circulating pump, the heating and cooling coils etc. – the continuous flow cooler, the temperature control as well as a special lighting device and a set of precision control thermometers.
Temperature bath and thermostat with cooling and heating coils and the circulating pump as well as the control unit are mounted inside the same housing. The temperature bath is equipped with a dual pane window made of flawless safety glass at the front and the back of the housing. Two different bath sizes may be supplied: Type 8100.0000 (24 l capacity) and type 8101.0000 (36 l capacity). Various liquids for the bath can be used (ref. to table on page 6), depending on the desired temperature range.
A lifting frame with an upper and lower plate serves for positioning the thermometers. In order to insert thermometers of various diameters and lengths – these plates are provided with different receiving holes and their vertical distance may also be adjusted. For holding the precision control thermometer a bushing with a rubber sealing ring is located in the top center of the housing. The opening at the top for inserting and removing the thermometers is covered by a plastic lid. All parts that are in contact with the bath's liquid are made of corrosion-resisting materials (stainless steel or chrome plated brass) – the seals are made of Viton. To the right of the actual temperature bath a separate chamber is located, housing the heating and cooling elements. The circulation of the liquid is provided by a SIMPLEX pressure pump without bearings. The exchange of the liquid between the bath and the chamber is designed in a way that the surface of the bath at a given level is always maintained - independent of the temperature and the number of thermometers under test (refer to Fig. 1: Functional principle).
The heating consists of 2 heating elements (coils), being connected to the temperature control.
The temperature control unit on top of the housing operates completely electronically, using a platinum resistance thermometer Pt 100 W. The desired temperature is preset by means of keys and displayed by a LED display. The accuracy of the preset temperature and the control accuracy is ± 0.1 K (fine tuning 0.01 K). All inputs are stored even when the unit is switched off or if supply fails.
The continuous flow cooler, type 8105.0000 works as an air-cooled refrigerator with a counter flow heat exchanger (ref. to fig. 2). As a separate external unit it is connected directly to the circulation of the bath's liquid by insulated hoses. The circulation of the liquid is achieved by means of the circulation pump of the bath. Two hose connections are installed at the right side of the bath housing. (Two additional hose connections at the rear side are connected to the cooling coil and provide a possible hook-up for a cryostat or cryomat in case a larger cooling capacity is required). By connecting the continuous flow cooler an intensive and constant cooling is achieved and bath temperatures down to
- 20°C (24 l bath type 8100.0000) or
- 10°C (36 l bath type 8101.0000) can be gained.
For illuminating the temperature bath a special
lighting device type 8114.0000 (24 l bath) or type 8115.0000 (36 l bath) is suitable. This lamp provides an illumination similar to daylight free from heat radiation – illuminating the whole area of the front inspection pane. As control thermometers (type 8117.0000) two mercury thermometers are used (depending on the desired range) – with a range of - 38°C...+ 10°C resp. - 1°C...+ 51°C, thermometer graduations are 0.1°C having standard ground joints and a prismatic capillary free from colour bands. The index is mounted according to the Richtersystem.
Instead of the thermometers a high precision PT100 (8117.0003) can be used.