Metrohm 774 Oven Sample Processor - Manual (Page 43)

4.1 Oven control
774 Oven Sample Processor, Instructions for use 37
4 Oven control and gas flow
In addition to the essential sample changer features, such as rotating the
sample rack and raising and lowering the lift, the 774 Oven Sample Proces-
sor also has a controllable sample heating block and a gas supply device.
This means that it is extremely suitable for applications in which moisture or
solvent vapors are to be driven out of a sample at an increased tempera-
ture and transferred to a measuring cell in a stream of carrier gas. The 774
Oven Sample Processor together with the Metrohm Coulometer or a
Metrohm KF Titrator and the suitable KF measuring cell form the ideal ana-
lytical system for the determination of water in samples which cannot be ti-
trated directly or only with great difficulty according to the conventional Karl
Fischer method.
4.1 Oven control
The oven heating block of the 774 Oven Sample Processor consists of a
solid aluminium block with a chromium steel jacket surrounding the sample
chamber. The sample chamber is intended for 22 mm x 38 mm sample vi-
als and allows samples of up to approx. 8 g to be heated up to 250 °C in a
very short time. The heating rate is up to 15 °C/min, depending on the tem-
perature range. The built-in fan quickly cools the oven down and supports
the accurate temperature control of the oven block.
The temperature control of the oven is functionally separate from the other
(sample changer) functions of the 774 Oven Sample Processor, i.e. the set
oven temperature remains constant (background control), even when other
functions or commands are carried out.
The required oven temperature can be set in three different ways:
• Initial temperature – an initial temperature can be set in the configura-
tion menu of the 774 Oven Sample Processor. As soon as the instru-
ment is switched on the temperature control is activated and the oven
heats up to the required (initial) temperature. The value of the initial tem-
perature remains stored in the instrument and can be used by the man-
ual HEATER function or the programmable HEATER command.
<CONFIG> key
Configuration
>oven settings
initial temperature 110°C
• Manual HEATER function – the oven temperature can be set manually to
any required value. When the <HEATER> key has been pressed the
required temperature and the duration of the heating-up phase can be
entered. If no heating-up time is entered then the full heating power will
be used to reach the required temperature as quickly as possible; this
temperature is then maintained.
<HEATER> key
HEATER: 110°C 10 min or
HEATER:init°C min