Casella CEL Thermohygrograph standard User Manual

THERMOHYGROGRAPH standard	June 2000
User Manual

THERMOHYGROGRAPH standard

User Manual

HB 3083-02

COPYRIGHT

The copyright in this document, which contains proprietary information, is vested in CASELLA CEL. The contents of this document must not be used for purposes other than that for which it has been supplied or reproduced or disclosed wholly or in part without the prior written permission of

CASELLA CEL

CASELLA CEL		CASELLA USA
Regent House		17 Old Nashua Road #15
Wolseley Road		Amherst
Kempston		NH 03031
Bedford		U.S.A.
MK42 7JY		Toll Free:	[phone]
Phone:	[phone]	Fax:	[phone]
Fax:	[phone]	e-mail:	[e-mail]
E-mail	[e-mail]	Web:	www.casellausa.com
Web:	www.casellagroup.com

Contents	THERMOHYGROGRAPH standard
	User Manual

TABLE OF CONTENTS

CONTENTS . . . . . . . . . . . . . . . . PAGE

1.	INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . .		3
2.	PRINCIPLE OF OPERATION . . . . . . . . . . . . . . . . . . . .		4
	2.1	Humiditity Measurement . . . . . . . . . . . . . . . . .	4
	2.2	Temperature Measurement . . . . . . . . . . . . . . . .	4
	2.3	General . . . . . . . . . . . . . . . . . . . . . . . . . . .	4
3.	PREPARATION FOR USE . . . . . . . . . . . . . . . . . . . . . .		5
	3.1	Removing/Replacing the Drum . . . . . . . . . . . . . .	5

3.2Fitting/Replacing the Battery. . . . . . . . . . . . . . . . 5

3.3 Setting the Clock speed. . . . . . . . . . . . . . . . . . . 5

3.4Fitting/Replacing the Chart. . . . . . . . . . . . . . . . . 6

3.5 Fitting/Replacing the Pens. . . . . . . . . . . . . . . . . . 6

4.	OPERATING THE INSTRUMENT . . . . . . . . . . . . . . . . . .		8
5.	MAINTENANCE & SPARES . . . . . . . . . . . . . . . . . . . . .		9
	5.1	Routine Care . . . . . . . . . . . . . . . . . . . . . . . .	9
	5.2	Quarz Clock . . . . . . . . . . . . . . . . . . . . . . . .	9
	5.3	Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . .	9
	5.4	Service . . . . . . . . . . . . . . . . . . . . . . . . . . .	9

5.5Spare Parts. . . . . . . . . . . . . . . . . . . . . . . . 10

6.

SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . .

11

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THERMOHYGROGRAPH standard	Introduction
User Manual

1.INTRODUCTION

This handbook introduces you to the basic operation and features of the

CASELLA standard THERMOHYGROGRAPH.

Thermohygrographs are used to produce a continuous record of the variation of both the temperature and relative humidity of the atmosphere against time, by drawing coloured traces on a chart.

Variations in relative humidity can affect many manufacturing processes, storage of raw materials, weights of items such as wool, paper, tobacco, confectionery, and computer operation, as well as being an important factor in human comfort. Since temperature is often linked to changes in relative humidity, this instrument records both on a single chart.

The THERMOHYGROGRAPH standard model may be ordered with or without a calibration certificate.

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Principle	THERMOHYGROGRAPH standard
	User Manual

2 PRINCIPLE OF OPERATION

2.1Humidity Measurement

The element that senses relative humidity is made from several strands of specially treated human hair, which shorten as relative humidity decreases and lengthen as it increases. The relative humidity element is connected through a linkage to the pen arm so that changes are recorded as an ink line on the chart. The linkage is designed to give a near linear movement over most of the chart range.

2.2Temperature Measurement

The temperature element is a bi-metalic strip, whose curvature depends on the current air temperature. As the temperature changes, the angular position of the free end of the strip changes. The free end is connected via a linkage to the pen arm so that changes are recorded on the chart.

2.3General

Relative humidity and temperature are recorded on the same chart, so to distinguish between the two traces, the temperature pen is black while the relative humidity pen is red.

To allow the pens to pass each other without colliding, the black temperature arm is shorter than the red relative humidity arm. This also means that the two traces are displaced in time with respect to each other, with the red trace indicating the correct time.

Fibre tipped pens are supplied which contain sufficient ink in the body to write for approximately 9 months. Replace the pen when the trace grows too faint to read.

Relative humidity is always scaled from 0 - 100%.

The temperature span for the THERMOHYGROGRAPH standard is 50oC, and this can be set to cover two alternative ranges: -10 oC to +40oC or 0oC to +50oC.

When the instrument is dispatched, a special chart is fitted that gives instructions for changing the temperature offset to match the range of the chart selected. The unit is factory calibrated for 0 oC to +50oC.

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