Temperature Measurements; Decibel Measurements; Remote Control - Hameg Instruments HM8012 Handbuch

a DC voltage across the connection terminals.
Accordingly, only voltage-free objects need to
be measured because any additional voltages in
the measurement path will distort the result. It is
preferable to remove, if necessary, any compo-
nents connected to the semiconductor for precise
results. It is possible to measure voltages up to 5
V. The maximum voltage that the equipment will
supply is 10 V in an open circuit. If the cathode
of the DUT is connected to the ground (COM-
terminal), the diode operates in its conducting
mode. If the anode of the DUT is connected to
ground, the diode operates in its reverse mode.
For measurements on Zenerdiodes, the anode of
the device should be connected to ground. Take
care when making measurements on sensitive
circuits. The current supplied by HM8012 is
1 mA constant for this function. All keys except
, and HOLD/OFFSET
for this function.

Temperature measurements

Choose the temperature measurement function
(°C or °F) using ,
probe is connected between the COM terminal
and the V/ /T°/dB terminal
Temperature measurement requires a tempera-
ture probe type PT100 as per standard EN60751.
The use of another probe is possible but can
generate additional errors due to a different link
cable resistance. All keys except
HOLD/OFFSET are inactive for this function.
After the instrument has been turned-on, the
line resistance value of the temperature probe is
automatically compensated.
On starting, simultaneously pressing BEEP
and OFFSET will eliminate probe cable resi-
stance compensation (zero value). In all cases,
compensation can be carried out by setting the
probe to a temperature of 0 °C and using the
OFFSET function.
Note: Measurement of the temperature probe
line resistance should be made on the same in-
strument used for temperature measurements.
Only this procedure guarantees the specified
measurement error.
are inactive
key. The temperature
.
, and
R e m o t e c o n t r o l

Decibel measurements

Choose the decibel measurement function using
, key. For decibel measurements, the
unknown input voltage is connected between the
COM terminal and the V/ /T°/dB terminal.
The HM8012 is used for DC or AC voltage
measurements in decibels. The 0 dB reference
is defi ned for 1 mW power in a 600 load., i.e.
a voltage of 0.7746 V. The scale extends from
–78 dBm to 59.8 dBm.
In a 50 -system, the reference voltage for 1mW
power is 0.2236 V. In a 75 -system, the reference
voltage for 1 mW power is 0.2739 V.
If decibel measurements are made on a 50 -
system, add 10.8 dB to the displayed value. If
decibel measurements are made on a 75 -system,
add 9 dB to the displayed value. The mathematical
relationship is as follows:
R= Reference resistance in ; P
Sign consideration: A displayed value of –12 dB is
equivalent in 50 to: –12 dB +10.8 dB = –1.2 dB

Remote control

HM8012 includes a front panel connector
controlling the equipment by means of a point-
to-point serial link. There are 3 wires used: RxD
(Receive Data), TxD (Transmit data), SGnd (Signal
Ground). The signal voltage levels must comply
with the following levels (±15 V max., ±3 V min.).
The link is of the bi-directional asynchronous type
with a fi xed confi guration: 4800 Baud, 8 bits, no
parity, one stop bit. The synchronization protocol
is XON/XOFF (half duplex) and is also fi xed.
Each control must have two ASCII code characters
followed by character 13 (symbolized as <CR> in
ASCII) or two characters 13 and 10 (symbolized as
<CR> <LF> in ASCII), while the <LF> character
is ignored during reception.
The instrument internal buffer includes only
three characters, and there is no way of sending
Subject to change without notice
= 1 mW; V in V
0 0
for
29