Field-test Dew point

Transcription

1 Field-test Dew point Type (Ex) / (Non-Ex) Operating Manual BA BARTEC GmbH Schulstraße 30 Postfach 63 D Gotteszell Phone ( ) Telefax ( ) info@go.bartec.de Internet:

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3 Contents C - 1 Table of contents Contents Page Issue date 1 Description Task Operating principle Ordering details Sources of errors 2 2 Start-up 3 3 Measuring Requirements Preparing the measurement Carrying out the measurement 7 4 Measurement correction 9 Conversion table for Field-test Dew point 11 All rights reserved and subject to change. Duplication, processing and distribution of this document, including parts thereof, is prohibited without the prior written consent of BARTEC. Copyright 2004 by BARTEC Schulstraße 30, D Gotteszell Document: BA valid from: Revision: Author: Walter Sturm Translation: E. Bauernfeind Nov. 2004

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5 Description 1 1 Description 1.1 Task Measurement systems and devices need to be inspected in regular intervals. The depth of these checks depends on the operating conditions as well as on the metrological features of the measurement system itself. For the field test of the humidity measurement system HYGROPHIL F 5672, BARTEC recommends the Field-test Dewpoint, by means of which function and stability can easily be verified. If it should turn out that for example due to an irremovable film on the sensor, the measured value has to be corrected, Field-test Dewpoint provides for the required correction factor. This method, which is particularly easy and practicable for measurements of residual humidity, is based on long years of experiences with the application of HYGROPHIL F 5672, which prove that a one-point-correction is absolutely sufficient in many applications (s. chapter 4). 1.2 Operating principle The Field-test Dewpoint works according to the principle of the saturated saline solution. Excessive salt makes sure that there is a constant relative humidity in the closed measuring chamber. For Field-test Dewpoint this amounts to 10 %, which stay constant in a large temperature range. By knowing the relative humidity and precisely measuring the temperature, you can calculate further humidity values. In the field test of HYGROPHIL F 5672, the dewpoint (DT) is calculated in C and, if required, is used for the correction in the device. This quite simple method offers a possibility to carry out a field test of the sensor technology with a satisfactory precision, provided that some conditions are observed: The constructive design of the measuring device has to be adapted to the on-site requirements. A stable and homogeneous temperature has to be guaranteed. Temperature measurement in the measuring chamber has to be as precise as possible and should also be possible in the Ex range. 1.3 Ordering details Designation Type Specification Contents Order no. Field-test Dewpoint Field-test Dewpoint Humidity standard generates dewpoint of - 10 at 23,3 C in the measuring chamber Check and adjustment in use through nominal/actual value comparison Ex range EEx ib IIB T Humidity standard generates dewpoint of - 10 at 23,3 C in the measuring chamber Check and adjustment in use through nominal/actual value comparison Non-Ex range Measuring chamber with temperature compensation and built-in Pt 100 Class A Precision thermometer ±0,1 C, portable device EEx ib IIB T4 Portable complete set in the service box Measuring chamber with temperature compensation and built-in Pt 100 Class A Precision thermometer ±0,1 C, portable device Portable complete set in the service box

6 Description 2 Measuring chamber with PT 100 Protective tube against draught Sealing for adapter Adapter for L 1631 Standing ring Humidity standard Precision thermometer Screw feet for standing ring Components of Field test Dewpoint in the service box 1.4 Sources of errors The easy handling of Field-test Dewpoint must not tempt the user to ignore two potential sources of errors: 1. In the measuring chamber, the temperature of the sensor and the temperature of the humid air have to be as identical as possible. A temperature difference of 1 Kelvin can result in an error of up to 3 % of relative humidity. For an ambient temperature of 20 C, this results in the following error limits: RH 10 % = > -12,5 C DT = nominal value RH (10-3) % = > -16,9 C DT RH (10+3) % = > -9,2 C DT 2. The second source of error is an unstable temperature. This is caused if - the read-out takes place too early, or - due to unfavourable placement, e.g. at a draughty place, there is a permanent fluctuation of the temperature in the measuring chamber, or - read-out and adjustment at the device do not take place simultaneously or almost simultaneously. An error of 1 C TT leads to the following results: TT 20 C = > -12,5 C DT = nominal value TT (20+1) C = > -11,8 C DT TT (20-1) C = > -13,3 C DT

7 Start-up 3 2 Start-up Before starting the first measurement the measuring chamber has to be filled up with the humidity standard. To this the measuring chamber is held with the left hand and unscrewed clockwise with the right hand. The humidity standard contains 5 ampoules and 6 pads. Ampoules Pads Put a pad in the round notch at the bottom of the measuring chamber (which consists of four single sheets). Break off the head of an ampoule under slight pressure. Use protective gloves for it absolutely and keep the ampoule head faceup.

8 Start-up 4 Then dribble the whole ampoule contents on the pad. Subsequently screw the bottom and top of the measuring chamber together again by hand.

9 Measuring 5 3 Measuring 3.1 Requirements 1. The most important requirement for an accurate measurement: In the moment of the measurement, the temperature at the tip of the humidity probe and the gas temperature in the measuring chamber have to be identical. 2. The read-out of the temperature in the measuring chamber and the entry of this temperature into the evaluation unit HYGROPHIL F 5672 have to take place almost simultaneously; the temperature in the measuring chamber must not change within this time. Please note before the measurement To make sure that the test is successful, it is required by any means that there are stable and balanced temperature conditions in Field-test Dewpoint and its environment. How can this be achieved in a real environment? Protect the measurement device against every factor that can cause temperature changes. By any means, it has to be shielded from draught, solar radiation etc. Some tips : Look at the environment as if instead of Field-test Dewpoint you yourself were sitting there in a wet bathing suit. Put Field-test Dewpoint on an insulating base, e.g. a piece of styrofoam, a wooden board, a jacket. If the measuring spot is draughty, wrap Field-test Dewpoint into a cloth or a jacket. If the measurement is in open air, provide some shadow for the protective tube. This is even necessary when the sky is cloudy, as the sun can be very strong even behind the clouds. Take your time! Assume one hour per measuring procedure. Even when the temperature display is steady, there are still some compensatory mechanisms in the measuring chamber.

10 Measuring Preparing the measurement 1 Take the humidity probe out of the process. 2 Check the probe visually for soiling or damages. 3 If required, clean the probe with a painting brush or with a soft cloth and some Isopropanole. Make sure that no water hides in the probe tip. 4 Mount the probe in the measuring chamber. 4.1 By means of an open-end wrench (13 mm), loosen the cover of the measuring chamber and take it off. 4.2 Slowly insert the humidity probe as far as it will go and pull it out again for 2-3 mm so that it does not bump against the bottom of the measuring chamber. 4.3 Slightly tighten the fastening nut. This should be done quickly to make sure that as little humidity as possible gets into the measuring chamber from outside, as this would prolong the waiting time. 4.4 Establish the connection between Pt100 and the precision thermometer. 5 Place the measuring chamber in the protective tube. 5.1 Take off the lid of the protective tube. 5.2 Mount the screw feet and put the protective tube onto the standing ring. 5.3 Put the measuring chamber onto the protective tube. 5.4 Lead the connection cable of the Pt 100 through the cut-out in the protective tube. Now the measuring chamber is in a container with balanced temperature conditions.

11 Measuring Carrying out the measurement When the conditions in the measuring chamber seem to be stable, the actual evaluation is carried out. On the sensor side Read the temperature at the precision thermometer. Make no changes at the measuring chamber and at the protective tube and go immediately to the evaluation side On the evaluation side Disconnect the automatic temperature input and the pressure input. You find both of them on the rear of the evaluation unit HYGROPHIL F Remove the connection wires at the terminals for the inputs of the temperature sensor and the pressure sensor. Device type Terminal designation T+ and P+ at the 12-pole plug /-30 TEMP I+ und PRESS I /31 TEMP 1, 2 und PRESS 6 Now the device is ready for the manual input of temperature and pressure. Make sure that temperature and pressure appear in the lower line of the display. If in this line the wave length is displayed instead of temperature and pressure, press [F2] to switch over to this display. The values for temperature and pressure which are then displayed are the stored fixed values. Note both values, as you will have to enter them again after the test has been completed.

12 Measuring 8 Pressure value input Press the [SP] key. The display shows the selection of pressure units. The number of the currently set pressure unit is underlined and the flashing cursor is at this position. Press [ENTER]. The currently set pressure at the measuring point is indicated. Now enter the atmospheric standard pressure (1013 hpa). Enter the new value by using the numeric keys ([0]...[9]). Entries can be deleted with the [CLEAR] key if you need to make any corrections. The cursor then returns to the beginning of the line and you can repeat the entry. To adopt the newly entered value, press [ENTER]. The unit then returns to display mode. Temperature value input Press the [TT] key. 12,9 C The display will show the temperature value currently stored in the evaluation unit. Enter the temperature that was indicated at the precision thermometer of Field-test Dewpoint. Enter the new value by using the numeric keys ([0]...[9]). Entries can be deleted with the [CLEAR] key if you need to make any corrections. The cursor than returns to the beginning of the line and you can repeat the entry. To adopt the newly entered value, press [ENTER]. The unit then returns to display mode. Calculating the deviation of DT In the table on p. 8, select the value for DT belonging to the entered temperature value (TT). Press the [DT] key at the evaluation unit. The dewpoint temperature DT is displayed. Compare the displayed value with the value calculated from the table. If the value does not deviate by more than ± 2 C, there is no need to act. The tolerance is within the precision this test can provide. If the value deviates by more than ± 2 C, you have two possibilities: 1. Send the complete system to the plant for recalibration. 2. Carry out the offset procedure. You find the description in chapter 4 or in the user manual of the evaluation unit. At the precision thermometer, you read a temperature of 12,9 C (TT). From the table on p. 8, it follows that there is an appropriate value of -18 C for DT. At the evaluation unit, a dewpoint temperature DT of -16 C is displayed. The required change of the offset setting is -2 C. The settings shown in chapter 4 refer to this example.

13 Measurement correction 9 4 Measurement correction Measurement correction is carried out by changing the offset settings in the programming mode. Call up programming mode Password Selecting the menu To call up the programming mode, press the [PROG] key at the 5672 evaluation unit. After calling up the programming mode you will first be asked for the password. To make any changes to the program you must enter the correct password. The password is: Press [ENTER] twice, so the menu EQUIP.-CONF.? is displayed. Press [1] [ENTER], to open the menu EQUIP.-CONF.. Now press [ENTER] several times until the menu OFFS-CAL? appears. [1] [ENTER] Õ Call up offset setting function After the offset setting function is called up, the date of the last offset change is indicated. Enter the current date in the form 20,06,2004 and confirm it by pressing [ENTER]. 12,9 C 1.0 bar The current values for temperature and pressure will be indicated. Confirm them with [ENTER]. SETPOINT: DT= C The current measured value is presented under the readout "SET- POINT". SETPOINT: DT= C Enter the value for DT that you have found in the table and confirm it with [ENTER]. OFFSET DT= -2.0 C The offset setting is indicated in the measurement variable's unit of measurement. Confirm it with [ENTER]. The offset setting is indicated in the wave length shift. Confirm it with [ENTER]. The evaluation unit exits the programming mode and switches to display mode, returning to the operating mode last set there.

14 Measurement correction 10 Now re-enter the original fixed values for temperature and pressure (see. page 8 Pressure value input and Temperature value input). Connect the temperature and the pressure sensor to their terminals at the rear of the evaluation unit.

15 Conversion table 11 Conversion table for Field-test Dew point The temperature displayed on the thermometer leads to the corresponding Dew point temperature DT (rated value) at RH = 10%. TT DT TT DT TT DT TT DT TT DT TT DT 5,0-24,2 9,5-20,7 14,0-17,2 18,5-13,7 23,0-10,2 27,5-6,8 5,1-24,1 9,6-20,6 14,1-17,1 18,6-13,6 23,1-10,2 27,6-6,7 5,2-24,0 9,7-20,5 14,2-17,0 18,7-13,5 23,2-10,1 27,7-6,7 5,3-23,9 9,8-20,4 14,3-16,9 18,8-13,5 23,3-10,0 27,8-6,6 5,4-23,8 9,9-20,3 14,4-16,9 18,9-13,4 23,4-9,9 27,9-6,5 5,5-23,8 10,0-20,3 14,5-16,8 19,0-13,3 23,5-9,9 28,0-6,4 5,6-23,7 10,1-20,2 14,6-16,7 19,1-13,2 23,6-9,8 28,1-6,4 5,7-23,6 10,2-20,1 14,7-16,6 19,2-13,2 23,7-9,7 28,2-6,3 5,8-23,5 10,3-20,0 14,8-16,5 19,3-13,1 23,8-9,6 28,3-6,2 5,9-23,5 10,4-20,0 14,9-16,5 19,4-13,0 23,9-9,6 28,4-6,1 6,0-23,4 10,5-19,9 15,0-16,4 19,5-12,9 24,0-9,5 28,5-6,1 6,1-23,3 10,6-19,8 15,1-16,3 19,6-12,9 24,1-9,4 28,6-6,0 6,2-23,2 10,7-19,7 15,2-16,2 19,7-12,8 24,2-9,3 28,7-5,9 6,3-23,1 10,8-19,6 15,3-16,1 19,8-12,7 24,3-9,3 28,8-5,8 6,4-23,1 10,9-19,6 15,4-16,1 19,9-12,6 24,4-9,2 28,9-5,7 6,5-23,0 11,0-19,5 15,5-16,0 20,0-12,6 24,5-9,1 29,0-5,7 6,6-22,9 11,1-19,4 15,6-15,9 20,1-12,5 24,6-9,0 29,1-5,6 6,7-22,8 11,2-19,3 15,7-15,8 20,2-12,4 24,7-8,9 29,2-5,5 6,8-22,7 11,3-19,3 15,8-15,7 20,3-12,3 24,8-8,9 29,3-5,4 6,9-22,7 11,4-19,2 15,9-15,7 20,4-12,2 24,9-8,8 29,4-5,3 7,0-22,6 11,5-19,1 16,0-15,6 20,5-12,2 25,0-8,7 29,5-5,3 7,1-22,5 11,6-19,0 16,1-15,5 20,6-12,1 25,1-8,6 29,6-5,2 7,2-22,5 11,7-18,9 16,2-15,4 20,7-12,0 25,2-8,6 29,7-5,1 7,3-22,4 11,8-18,9 16,3-15,3 20,8-11,9 25,3-8,5 29,8-5,1 7,4-22,3 11,9-18,8 16,4-15,3 20,9-11,9 25,4-8,4 29,9-5,0 7,5-22,2 12,0-18,7 16,5-15,2 21,0-11,8 25,5-8,3 30,0-4,9 7,6-22,1 12,1-18,6 16,6-15,1 21,1-11,7 25,6-8,3 7,7-22,1 12,2-18,6 16,7-15,0 21,2-11,6 25,7-8,2 7,8-22,0 12,3-18,5 16,8-14,9 21,3-11,5 25,8-8,1 7,9-21,9 12,4-18,4 16,9-14,9 21,4-11,5 25,9-8,0 8,0-21,8 12,5-18,3 17,0-14,8 21,5-11,4 26,0-8,0 8,1-21,7 12,6-18,2 17,1-14,7 21,6-11,3 26,1-7,9 8,2-21,7 12,7-18,2 17,2-14,6 21,7-11,2 26,2-7,8 8,3-21,6 12,8-18,1 17,3-14,6 21,8-11,2 26,3-7,7 8,4-21,5 12,9-18,0 17,4-14,5 21,9-11,1 26,4-7,7 8,5-21,4 13,0-17,9 17,5-14,4 22,0-11,0 26,5-7,6 8,6-21,4 13,1-17,9 17,6-14,3 22,1-10,9 26,6-7,5 8,7-21,3 13,2-17,8 17,7-14,2 22,2-10,9 26,7-7,4 8,8-21,2 13,3-17,7 17,8-14,2 22,3-10,8 26,8-7,3 8,9-21,1 13,4-17,6 17,9-14,1 22,4-10,7 26,9-7,3 9,0-21,0 13,5-17,6 18,0-14,1 22,5-10,6 27,0-7,2 9,1-21,0 13,6-17,5 18,1-14,0 22,6-10,6 27,1-7,1 9,2-20,9 13,7-17,4 18,2-13,9 22,7-10,5 27,2-7,0 9,3-20,8 13,8-17,3 18,3-13,9 22,8-10,4 27,3-7,0 9,4-20,7 13,9-17,2 18,4-13,8 22,9-10,3 27,4-6,9 aligned to DIN

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