LB-720 CONTROL SYSTEM FOR DYNAMIC AIR DRIERS

precise and quick humidity measurement regulation of dryer's work regulation of heater's work

Description

• relative humidity and air temperature meter - hytherograph LB-710M2,
• control - processing device - humidity controller LB-722,
• remote control device - programmer LB-721.

The whole set is used for relative humidity regulation in closed rooms in cooperation with a dynamic air drier (DOP) - which realizes the blow-in of dried air.

Thermometer - hygrometer LB-710M is an independent device equipped with a relative humidity capacity sensor and a sensor Pt-1000 sensor used for temperature measurement. Thermometer - hygrometer LB-710M2 has a microprocessor, which realizes measurement algorithms that take into consideration (nonlinear) characteristics of both elements and calibration data stored in a nonvolatile memory. The measurement results are transmitted to a regulator LB-722 in a digital form with the speed of approx. 300 bods and measurement repetition period approx. 2s. Type of current interface used allows on powering the device at the same time. This type of solution guarantees simple hytherograph - regulator connection - using only two cables. both devices can be placed
considerably far away from each other (limited only by the connecting cable loop's resistance - less than 100 ohm). Because of a low transmission speed and a current interface standard, the cable which connects a servo with a hytherograph can be of any type as long as its high resistance to outside interference is secured. The connection is also resistant to changing the cable's terminals (polarity).

During hytherograph LB-710M2 periodical calibration (confirmation) a two way digital transmission is used. Throughout calibration a set of coefficients that grade the results is stored in the nonvolatile memory of the hytherograph LB-710M. All regulation elements were eliminated (potentiometers and trimmers) since they often cause problems (thermal instability, static and noises, accidental change in settings etc.).

Each thermometer – hygrometer LB-710M2 (upon a request) can have an individual calibration certificate issued by the Central Army Metrology Center in Zielonka or from the LAB-EL Calibration Laboratory.

Thermometer – hygrometer LB-710 has a certificate of type RP T 95 77 issued by the President of Central Measurement Office in Warsaw. Thermometer – hygrometer LB-710 is a different version of a hytherograph LB-710M2 in which less expensive electronic elements were used with limited scope of work temperatures from 0°C to +70°C.

The humidity regulator LB-722 receives the relative humidity and temperature results taken from a chosen part of the object from the attached to it hytherograph LB-710M2. After exceeding the relative humidity or temperature set thresholds (in a version LB-720T) the regulator using transmitter output switches on a drying device or a heater. It realizes two stage humidity and temperature regulation. The regulation hysteresis set for humidity equals 2%, which means that a drier is switched on when the measured relative humidity goes below 2% of the set limit.

The regulator LB-722 counts the actual time of the dryer's work (the so called "motohours") and allows (upon a request) on displaying this time in hours. The regulator LB-722 registers in its memory the results of the last 64 relative humidity measurements performed every hour. The motohour meter, humidity measurement results and the set regulator work parameters (humidity thresholds) set by service people are stored in the device's nonvolatile memory which is resistant to lack of power supply.

The actual measurement results, the motometer's state, the measurements stored in the last 64 hours and the device's settings are shown on two four digit LED displays (a digit's height is 12 mm). The displays can work in different work modes. In the basic mode the actual humidity and temperature measurement results are shown. When programming the device one of the displays shows the set parameter and the other one an adequate description (symbolic marking for parameter). A similar situation takes place when displaying the motohour's meter and browsing the measurement results' memory (in the last case one of the displays shows - symbolically - time and the other one stored humidity measurement result).

Regulator LB-722 is equipped with a digital output, which is used for transmission of the actual temperature and humidity measurement results, with a speed of 300 bps, with intervals of approx. 2s. The output works in a standard similar to hytherograph LB-710M2. LB-710M2 as well as servos DOP LB-720. A simple system with one or two hytherographs or servos can be obtained by connecting them to IBM computer ports COM1 / COM2 using signal conversion sets (current - voltage LB-370) produced by LAB-EL company. A greater number of system elements can be attached using a concentrator LB-731 also produced by LAB-EL company, interface, what allows on simple creation of a computerized system which monitors the environmental conditions in many rooms. Such system can include any number of hytherographs

Programmer LB-721 is a remote control transmitter used for programming the regulator LB-722 settings using optic connection (IR). it especially regulates the following:

• threshold for switching on a drying and heating unit,
• threshold for switching off a unit (such as: humidity value, below which the function "blow-in" is also blocked),
• humidity alarm threshold.

The settings are stored in the regulator LB-722 nonvolatile memory (the latest chosen values stay the same after switching off the power supply). Additionally the programmer allows on browsing the memory, with the last 64 measurement results as well as controlling the motohour meter stage.

Such way of programming the device secures the device settings from any changes done accidentally or on purpose by unauthorized staff (a special pilot LB-721 has to be used). It also allows on eliminating the programming switches (it is hard to make them water tight). The programmers range amounts to approx. 1m.

The programmer LB-721 is a small portable ("pocket") device, powered from one battery 9 V (6F22). It is equipped with an easy to read 8 key button membrane keyboard. Six key buttons switch the servo's work mode (according to a description enclosed) switching on one of the setting modification modes. the remaining two are used for increasing or decreasing the parameters during the process of programming.

The construction solutions used in all devices allow on obtaining wide scope of work temperatures (-40..+70 °C). They also assure high resistance to interference and reliability. Especially all three devices (LB-710M2, LB-722, LB-721) were built basing on the microprocessors especially accustomed to work in such conditions. All plastics used for making the device's casing can resist thermal exposure in the scope of temperatures -40..+80 °C.

Technical data

OUTPUT CAPACITY "ALARM" AND "DRIER"

POWER SUPPLY (without alarm signaling)

Produced by: LAB-EL Laboratory Electronics 68b, Bodycha Str., 02-495 Warsaw tel: (022) 667 71 18, 0601 209656, fax: (022) 867 53 32 e mail: info@label.com.pl home page: http://www.label.com.pl internet meteorological station: http://www.meteo.waw.pl meteorological station on a mobile phone: wap.meteo.waw.pl Last updated: 17.03.2006