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the pointer of an analogue measuring instrument but without its
mechanical disadvantages. It is particularly suitable for quickly-chan-
ging signals, for which the digital display is too "slow". Trends in a
changing measurement value can thereby be quickly recognised and
evaluated. During overrun or when the measurement range is excee-
ded, all bar graph display segments flash.
H) Logic test
This measurement function indicates logic levels in digital circuits.
1. Switch the measuring instrument on.
2. Set the measurement function switch (8) to HIGH/LOW. "rdY"
(ready) appears in the display.
3. Connect the test leads to the COM socket (black lead) and to the
V/Ω socket (red lead).
4. Now connect the other end of the black test lead to the digital cir-
cuit"ground" = "-" (normally). The red test probe must be connec-
ted to the positive supply voltage (V+ or Vcc).
5. When the connections are made, press the Set/Reset button once.
6. While the black test lead remains connected to ground, the red test
probe can be removed from the positive supply. The test points
under consideration can now be touched with the red test probe; as
a result the multimeter will display three possibilities.
- If the level is more than 70 % of the stored supply voltage, "Hi"
will be displayed;
- If the level is less than 30 % of the stored supply{1215} voltage,
"Lo" will be displayed;
- If the level on the contrary is between = 31 % and 69 % of the sto-
red supply voltage (e.g. 5 V), "---" will be displayed.
In the "LOGIC" operating mode, it is not possible to use the subfunctions
"MAX", "MIN" and Data Hold = "D-H". Before using the measurement
range switch when leaving the logic function, -the SET/RESET button
must be pressed, so that "rdY appears" in the- display.
I) Using the multimeter in connection with a computer
a) Connection
Connect the RS-232 interface cable (null modem cable) to the mul-
timeter (rear of the case under the lower cover) and to a serial inter-
face of the computer.
Now switch on the measuring instrument.
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b) Using the software
This multimeter operates with any computer with an RS-232 inter-
face, but the software is only suitable for IBM-compatible compu-
ters. Using the software is described as follows:
1. Insert the floppy disk into the drive. Copy the files either onto the
hard drive or make a back-up copy of the floppy.
2. Press the "Enter" key.
3. To stop or interrupt the program during execution, press CRTL +
BREAK on the computer keyboard.
Data transfer
SAs soon as the multimeter is switched on, the interface is ready. Data
transfer is started by command [D] from the computer.
The following should be noted, when software other than that provi-
ded is used.:
The data format is 14 bits in length. It is composed as follows:
BYTE 1 2 3 4 5 6 7 8 9 A B C D E
Example 1 DC
- 3 , 9 9 9
Example 2 OHM
3 , 9 9 9 M o h m CR
Program example in BASIC for easy reading of the multimeter:
10 OPEN "COM1:1200,N,7,2,RS,CS,DS,CD" AS#2
20 A$="D"
30 PRINT #2,A$;
40 IN$=INPUT$(14,#2)
50 PRINT IN$
60 CLOSE #2
70 END
Specific data transfer characteristics (communication parameters):
Transfer rate
: 1200 baud
Character code
: 7-bit ASCII
Parityt
: none
Stop bits
: 2
5.5 Maintenance and calibration
V
CR
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