Decibel Measurements; Equipment Remote Control; Function Commands - Hameg HM 8012 Manual

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 resistance
compensation (zero value). In all cases, com-
pensation 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 instrument
used for temperature measurements. Only this
procedure guarantees the specified measurement
error.

Decibel measurements

Choose the decibel measurement function using
(18) or (19) key. For decibel measurements, the
unknown input voltage is connected between the
COM terminal and the V/Ω/T°/dB terminal.
The HM8012 is used for DC or AC voltage
measurements in decibels. The 0 dB reference is
defined for 1mW power in a 600 Ω load., i.e. a voltage
of 0.7746V. The scale extends from –78 dBm to
59.8dBm.
In a 50Ω-system, the reference voltage for 1mW
power is 0.2236V. In a 75Ω-system, the reference
voltage for 1mW power is 0.2739V.
If decibel measurements are made on a 50Ω-
system, add 10.8dB to the displayed value. If decibel
measurements are made on a 75Ω-system, add 9dB
to the displayed value. The mathematical relationship
is as follows:
R= Reference resistance in Ω ; P
Sign consideration: A displayed value of –12dB is
equivalent in 50Ω to: -12dB +10.8dB = -1.2dB

Equipment remote control

HM8012 includes a front panel connector (13) for
controlling the equipment by means of a point-to-
point serial link. There are three 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 fixed configuration: 4800 Baud, 8 bits, no
parity, one stop bit. The synchronization protocol is
XON/XOFF (half duplex) and is also fixed.
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.
30
The instrument internal buffer includes only three
characters, and there is no way of sending more
than one command at a time. On reception of
terminator <CR>, the equipment sends the
character 19 (<DC3> ASCII) to indicate that the
dialogue is suspended. As soon as it is possible to
resume dialogue, the instrument sends character
17 (<DC1> ASCII).
The commands are divided into five groups:
These commands are used for choosing another
magnitude to be measured and corresponding to the
choice of FUNCTION key on the front panel.
VO<CR>
AM<CR>
MA<CR>
OH<CR>
DI<CR>
TC<CR>
TF<CR>
DB<CR>
For these commands, there is no error recovery
provided for because it is normally possible to put
the instrument in one of these states at any time.
Mode commands correspond to the "MODE" key
on the front panel.
DC<CR>
AC<CR>
=1mΩ; V in V
AD<CR>
0 0
BY<CR>
DN<CR>
If the requested mode is not compatible with the
current function (e.g.: sending the AC command
while the instrument is measuring resistances), the
instrument will indicate this by a beep in the same
way as for the front panel control. In addition, the
control error indicator is set (see command E7).
These correspond to the "RANGE" keys on the front
panel.
AY<CR>
AN<CR>
R+ <CR>
R- <CR>

Function commands

voltage measurement (VOLT)
current measurement (A)
current measurement (mA)
resistance measurement
diode test
temperature measurement in °C
temperature measurement in °F
measurement in dB.
Mode commands
switches the instrument to the
DC measuring mode.
switches the instrument to the
AC measuring mode.
switches the instrument to the
AC + DC measuring mode.
activates the continuity test beep.
deactivates the continuity test beep.
Range modification commands
switches to automatic range change
switches to manual range change
switches to the next higher range
switches to the next lower range.
Subject change without notice