EP0989373B1 - Device for producing a predetermined relative humidity in the air - Google Patents

Description

The present invention relates to a device for generating a defined relative humidity according to the preamble of claim 1.

With the increasing use of humidity sensors, for example in air-conditioning technology, there is a desire for devices by means of which such moisture sensors can be calibrated. Suitable devices for this purpose are also known under the term "humidity generators." These supply defined relative air humidity values RH in a measuring chamber in which, in turn, the humidity sensors to be calibrated or at least parts thereof can be arranged.
In addition to the ability to adjust the respective desired relative humidity over saline solutions according to DIN 50008, furthermore so-called two-pressure / two-temperature humidity generators have become known. In this case, air saturated with steam is generated in a saturator chamber at a temperature T1 and a pressure p1 and then expanded to a pressure p2 at the temperature T2 in a measuring chamber. By measuring the respective pressures pn and temperatures Tn, the relative humidity in the measuring chamber can be determined or in other words: by varying these parameters, the desired relative humidity RH can be defined in the measuring chamber. Reference is made to the publication "Humidity Sensing, Measurements and Calibration Standards" by PH Huang in Sensors, Feb. 1990, pages 12 to 21. The problem with such constructed humidity generators is now the relatively large outlay on equipment, in particular the temperature control, Temperature measurement and temperature stabilization to accomplish.
A less complex modification of such a moisture generator is now a so-called pure two-pressure generator. In this case, the temperature in the saturator chamber as well as in the measuring chamber is kept the same by suitable measures and the desired relative humidity RH merely by varying the pressure conditions in the Saturator chamber and the measuring chamber set. The relative humidity is thus a function of the ratio of p1 and p2, ie RH = f (p2 / p1), with only known, empirically determinable variables being included in this relationship. For such types of moisture generator, reference is made, for example, to JP 09-257283.
A disadvantage of the known two-pressure humidity generator from this document, however, is that the maximum saturated to RH = 100% air in the area between the saturator and the valve unit can condense and thus no more maximally saturated air is forwarded into the measuring chamber; However, this is assumed in the setting of the desired relative humidity RH on the pressure ratio of p1 and p2.

Object of the present invention is therefore a compact, possible simply constructed device for generating a defined relative Humidity to create, in particular, the above-mentioned problems be avoided in the moisture presentation.

This object is achieved by a device with the features in characterizing part of claim 1.

Advantageous embodiments of the device according to the invention result arising from the measures in the dependent claims.

The measures according to the invention now ensure an extremely compact and simply constructed device for generating a defined relative humidity. In addition, the above mentioned can also be Problems associated with the condensation of saturated air in the air Avoid the area of the connection line or valve unit.

Furthermore, the measures in the dependent claims ensure that in the entire range of relative humidity values to be displayed a constant Gas flow results in the measuring chamber. So varies from the above Reference known device at varying relative humidity values the gas flow in the measuring chamber. However, a constant gas flow is advantageous in terms of the overall accuracy of the system.

Thus, a device has been created which by simply varying the pressure conditions in the two chambers produce a desired relative humidity RH allows. In particular, the expenditure on equipment was significantly reduced compared to known humidity generators, so that ultimately results in a system that can be easily transported is.

In an advantageous embodiment, the inventive Measures used in a so-called two-pressure generator; in principle but is possible, even in the mentioned two-pressure / two-temperature humidity generators to realize these measures.

Further advantages and details of the device according to the invention result from the following description of an embodiment with reference to the accompanying drawings.

Figur 1

eine schematische Prinzipskizze eines Ausführungsbeispieles der erfindungsgemäßen Vorrichtung;

Figur 2a

eine detaillierte Darstellung der Heizeinrichtung aus Fig. 1;

Figur 2b

das elektrische Schaltbild der Heizeinrichtung aus Figur 2a;

Figur 3

eine Detailansicht der Ventileinheit aus Fig. 1;

It shows

FIG. 1

a schematic schematic diagram of an embodiment of the device according to the invention;

FIG. 2a

a detailed view of the heater of FIG. 1;

FIG. 2b

the electrical diagram of the heater of Figure 2a;

FIG. 3

a detailed view of the valve unit of FIG. 1;

An exemplary embodiment of the device according to the invention will be explained below with reference to the schematic illustration in FIG.
Thus, the device according to the invention for generating a defined relative humidity in this embodiment consists essentially of a single unit in which both the saturator chamber 1 and the actual measuring chamber 2 are arranged. The complete assembly is made of a material with high thermal conductivity. For example, aluminum is suitable for this purpose. The saturator chamber 1 is supplied on the input side via a supply line 3, for example, air under pressure p.
By means of a reducing valve 12, the setting of the desired pressure p1 in the saturator chamber 1 takes place, where p1 <p. In the saturator chamber 1 is water 1.1, which serves to saturate the air introduced or possibly nitrogen to the relative humidity RH = 100%. After saturation, the air is passed through a connection consisting of two sections 4.1, 4.2 connecting line and a valve unit 5 in the actual measuring chamber 2. The measuring chamber 2 in turn is connected via an open feed line 2.1 with the environment, ie in the measuring chamber 2 ultimately sets a pressure p2, which corresponds to the ambient pressure p _a .

About the defined setting of the pressure ratio p2 / p1 can be in the Measuring chamber 2 represent the desired relative humidity RH. In the measuring chamber 2 can then, for example, moisture sensors or at least Parts thereof are to be calibrated. The described Embodiment thus provides a two-pressure humidity generator group; As mentioned above, the inventive measures basically used in other types of humidity generator.

The device according to the invention further comprises in this variant two pressure measuring units 8, 9, via which the respective pressures p1, p2 in the saturator chamber 1 as well as in the measuring chamber 2 are detected exactly in such a way over the relationship RH = K * (p2 / p1) always the relative humidity RH to be able to determine. Here K represents an empirically determinable, constant Realgasfaktor dar. The output signals of the two pressure measurement units 8, 9 are used for the evaluation or further processing of a Operating unit 7 supplied in the above-mentioned relationship the relative humidity RH determined and displayed in a display area 7.1 becomes. In addition, the Bedieneineit 7 includes a control element 7.2, the Adjustment of the desired relative humidity RH in the measuring chamber 1 serves. About the control element 7.2 is ultimately on the reducing valve 12th so defined as to set the pressure p1 at which the air in the saturator chamber is saturated. About the setting of the pressure p1 and thus ultimately the pressure ratio p2 / p1 again results in the desired defined setting of the relative humidity RH in the measuring chamber 2. A corresponding signal connection line between the control unit 7 and the reducing valve 12 is also schematic in FIG indicated.

Furthermore, in the device according to the invention is a in Figure 1 schematically indicated heater 6 is provided which in thermal Contact with certain parts of the device is. This is located the heating device 6 on the one hand in thermal contact with the section 4.1 the connecting line between saturator chamber 1 and measuring chamber 2, which extends from the saturator chamber 1 to the valve unit 5. To the Others, the heater 6 is also in thermal contact with the valve unit 5. It is done so that heating of the connecting line section 4.1 and the valve unit 5 in order to condense the on RH = 100% saturated air in this area of the device, which ultimately constitutes a falsification of the in the measuring chamber 2 would cause relative humidity RH. Further details for the invention arranged heating device 6 will be described below with reference to the Figures 2a and 2b explained.

Figure 2a shows a partial view of the embodiment of Figure 1 with a more detailed view of the heater 6; FIG. 2 b shows an electrical circuit diagram of this heating device 6.
Visible is the section 4.1 of the connecting line between the saturator chamber 1 and the measuring chamber including the schematically indicated valve unit 5. The heater consists in the embodiment shown essentially of a current-carrying resistance wire, which in turn comprises two sections 6.1a, 6.1 b.
The first section 6.1a of the resistance wire is arranged around the connection line 4.1 in the region between the saturator chamber 1 and the valve unit 5. In the exemplary embodiment shown, the winding of the resistance wire 6.1a in this region of the connecting line was chosen such that approximately half the length of the resistance wire 6.1a in the first third of the connecting line 4.1, starting at the saturator chamber 1, was arranged.
The second section 6.1 b of the resistance wire, however, is arranged around the valve unit 5 wound. From the valve unit 5, a control element 5.3 is also recognizable in this illustration, via which optionally a setting of the desired gas flow into the measuring chamber 2 can take place.

To the area 4.1 of the connecting line and the valve unit 5 with the respective sections of the resistance wires 6.1a, 6.1b is further each one insulation 13 is arranged. This serves for thermal insulation these areas or the heater 6 with respect to the environment. As Isolation can be, for example, commercial PU foam or other commercial, prefabricated pipe insulation can be provided.

The two resistance wires 6.1a, 6.1b of the heater are connected in series in the illustrated embodiment and have contacts U _v , GND for connection to a suitable supply voltage. Furthermore, a contact UM is provided between the two resistance wires 6.1a, 6.1b, via which a control voltage can be tapped and consequently serves to check the function of the heating device.
The associated electrical equivalent circuit diagram for the exemplary embodiment of a heating device shown is shown in FIG. 2b. In one possible embodiment, in each case an electrical resistance of 100Ω was chosen in the two resistance wires 6.1a, 6.1b. The supply voltage applied to contact U _v is 24V; The heater is therefore formed in this embodiment as a simple constant power control. About such dimensioning or design of the heater can be in the range 4.1 of the connecting line and in the area of the valve unit 5, a heating of about 5-7 ° C reach, which is independent of the respective ambient temperature. The temperature in these areas is thus at least slightly above the dew point temperature of the saturated in the saturator chamber air. A condensation of the highly saturated air coming from the saturation chamber can be reliably prevented by these measures in these areas of the device according to the invention.

A detailed view of the valve unit 5 is shown in FIG. in this connection was for clarity on the presentation of the heater waived.

The valve unit 5 preferably comprises one in the present invention arranged on the input side, so-called. Differential pressure regulator 5.1, which is a needle valve 5.2 downstream, which in the embodiment shown further an adjustment 5.3 includes. The adjustment 5.3 of the needle valve 5.2 can be used to provide a desired gas flow in the Adjusting the measuring chamber.

The input side arranged in the valve unit 5 differential pressure regulator 5.1 now holds the reaching to the needle valve 5.2 air pressure p _z and thus the air flow in the measuring chamber constant, regardless of input side fluctuations of the air pressure p1 in the saturator 1. In the connecting line between the differential pressure regulator 5.1 and the Needle valve 5.2 in this case an intermediate pressure p _{z is} set, which is about 150 mbar above the pressure p2; the intermediate pressure p _z is kept constant. With the help of the needle valve 5.2 is a relaxation or expansion of the gas from p _z to p2, where p2 usually corresponds to the ambient pressure. As a result of the regulation according to the invention of the intermediate pressure p _z to the constant value p _z = p 2 + 150 mbar, a largely constant pressurization of the needle valve 5.2 is thus ensured independently of the set pressure p 1. Ultimately, such a largely constant mass flow is ensured by the valve unit 5 and a largely constant gas flow in the measuring chamber. This proves to be extremely advantageous, for example, for the desired calibration of humidity sensors in the measuring chamber if a constant gas flow is assumed during the calibration. Suitable differential pressure regulators 5.1 are available, for example, from Fischer & Porter under the name differential pressure regulator series 53R_2110 ".

The valve unit 5 consists of a differential pressure regulator 5.1, a needle valve 5.2 and optionally an adjusting device for the needle valve 5.3. By 5.1 is in the connecting line between 5.1 u. 5.2 set an intermediate pressure p _z of about 150 mbar over p2 and kept constant.

This intermediate pressure p _z is finally expanded to p 2 via the needle valve, where p 2 = p _a (ambient pressure) applies to p 2. By regulating the intermediate pressure p _z to a constant value p _z = p 2 + 150 mbar, a constant pressurization of the needle valve is ensured independently of the set pressure p 1, resulting in a constant gas flow in the measuring chamber.

In addition to the above explained with reference to an embodiment measures Of course, there are still alternative design options. For example, it is possible in particular, a differently constructed heater to use; so there is e.g. also made-up heating tapes, which could be used at this point. Likewise, in a more expensive embodiment, a temperature measurement also take place and the heating temperature can be set via a control, etc .. However, it is only decisive that both the first subregion of the connecting line as well as the valve unit in thermal contact with the respective heating device.

In addition, of course, there are other possibilities, such as about the concrete geometry of the two chambers as well as the respective Connection line can be executed etc ..

Claims (12)

1. Device for generating a defined relative humidity (RH), comprising a saturator chamber (1) and, connected thereto by means of at least one connecting line (4), a measuring chamber (2) in which the defined relative humidity (RH) can be adjusted merely by varying the pressures (p1,p2) in the saturator chamber (1) and in the measuring chamber (2), a valve unit (5) being additionally arranged in the connecting line (4.1,4.2),
   characterised in that
   both the valve unit (5) and the area of the connecting line (4.1) located between the valve unit (5) and the saturator chamber (1) are in thermal contact with a heating device (6;6.1a,6.1b).
2. Device according to claim 1, characterised in that there is substantially the same temperature in the measuring chamber (2) as in the saturator chamber (1).
3. Device according to claim 1, characterised in that the saturator chamber (1) is designed larger than the measuring chamber (2) and the measuring chamber (2) is integrated together with the saturator chamber (1) into a single basic unit.
4. Device according to claim 3, characterised in that the basic unit is produced from a material having high thermal conductivity.
5. Device according to claim 1, characterised in that the heating device (6,6.1a,6.1b) is designed in such a way that it can be used to adjust the temperature of the connecting line (4.1) and also of the valve unit (5) to be at least slightly above the saturation temperature of the air resaturated in the saturator chamber (1).
6. Device according to claim 1, characterised in that the heating device (6,6.1a,6.1b) is provided with a temperature control by means of which a certain heating power can be set.
7. Device according to claim 1, characterised in that the heating device (6,6.1a,6.1b) is designed in the form of a current-carrying resistance wire (6.1a,6.1b).
8. Device according to claim 1, characterised in that the valve unit (5) is designed to ensure a substantially constant stream of output gas emanating from the saturator chamber (1) even when the input gas pressure (p1) fluctuates.
9. Device according to claim 8, characterised in that the valve unit (5) has on the input side a differential pressure regulator (5.1), which has a downstream, adjustable needle valve (5.2).
10. Device according to claim 7, characterised in that an insulation (13) for providing thermal insulation is arranged around the area (4.1) of the connecting line which has the resistance wire (6.1a) wrapped around it, and around the valve unit (5).
11. Device according to claim 1, characterised in that an operational control unit (7) is additionally provided which includes at least one operational control element (7.2) for the defined adjustment of the relative humidity (RH) in the measuring chamber (2), as well as a display unit (7.1) for displaying the currently adjusted relative humidity (RH) in each case.
12. Device according to claim 11, wherein the operational control element (7.2), in order to adjust the defined humidity (RH), acts upon a reducing valve (12) which is arranged in the input-side supply line (3) of the saturator chamber (1).

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