7
A microprocessor controlled special tungsten lamp emits radiation
which is first optically conditioned and beamed to the sample contained
in the vial. The optical path is fixed by the diameter of the vial. Then
the light is spectrally filtered to a narrow spectral bandwidth, to obtain
a light beam of intensity
I
o
or
I
.
The photoelectric cell collects the radiation
I
that is not absorbed by
the sample and converts it into an electric current, producing a potential
in the mV range.
The microprocessor uses this potential to convert the incoming value
into the desired measuring unit and to display it on the LCD.
The measurement process is carried out in two phases: first the meter
is zeroed and then the actual measurement is performed.
The vial has a very important role because it is an optical element and
thus requires particular attention. It is important that both the
measurement and the calibration (zeroing) vials are optically identical
to provide the same measurement conditions. Most of parameters use
the same vial for both. In each case, insert the test vials always in the
same position into the holder.
It is necessary that the surface of the vial is clean and not scratched.
This is to avoid measurement interference due to unwanted reflection
and absorption of light. It is recommended not to touch the vial walls
with hands.
Furthermore, in order to maintain the same conditions during the
zeroing and the measuring phases, it is necessary to close the vial to
prevent any contamination.
74
Excel
©
Copyright of "Microsoft Co."
Lotus 1-2-3
©
Copyright of "Lotus Co."
TELIX
®
is registered Trademark of "Deltacomm"
Windows
®
and Windows Terminal
®
are registered Trademark of "Microsoft Co."
To connect your meter
to the PC use the optional
HI 920010
(available
from your Hanna Dealer). Make sure that your meter is switched off
and plug the connectors, one into the meter RS 232C socket, the other
into the serial port of your PC.
Note
: Cables other than
HI 920010
may use a different configuration,
in which case, communication between the meter and the PC
may not be possible.
SETTING THE BAUD RATE
The transmission speed (baud rate) of the meter and the external
device must be identical. The meter is factory set to 2400.
If you wish to change this value, please contact your nearest Hanna
Center.
SENDING COMMANDS FROM PC
With terminal programs such as, for example, Telix
®
, Windows Termi-
nal
®
, it is possible to remotely control your Hanna Instruments bench
meter. Use
HI 920010
cable to connect the meter to the PC, start the
terminal program and set the communication options as follows: 8, N,
1, no flow control.
Command Types
To send a command to the meter the scheme is:
<DLE> <
command>
<CR>
This line makes the computer send a Data Link Escape character (/ or
?), the command expressed as a number or a 3-character sequence
and a CR character.
Note:
Windows Terminal
®
and all the other terminal programs that
support the ANSI escape sequence, represent the DLE character
by the string ‘^P’ and the CR character by the string ‘^M’.
Type of Commands
/OFF - Turn the meter OFF
/PDR - Press Read Direct
/PTR - Press Timer
/PZR - Press Zero
INTERFACE WITH PC