Hameg HM 1004-3 Series, Manual

Page: 31 / 36

31
Subject to change without notice
Adjustments RS232 Interface - Remote Control
points in each circuit can be checked, and a defect can be
determined quickly and easily.
Possibly the device itself under test contains a reference
circuit (e.g. a second stereo channel, push-pull amplifier,
symmetrical bridge circuit), which is not defective.
Adjustments
As described in the “Menu” section, the instrument`s
software contains the submenu “CALIBRATE” . The controls
regarding the menus are described under item MENU (35) in
section “Controls and Readout”. After a warm up time of 20
minutes, the following items can be used by operators not
equipped with precision instruments.
Both items are regarding the instrument’s temperature
response under extreme environmental conditions. Similar
effects can be caused by component failures as a result of
the application of too high voltage at an input and therefore
cannot
be compensated by the automatic adjustment
procedure. During these automatic adjustments there must
be no signal applied to any input.
1. Y AMP ( Y amplifier)
Corrects trace position changes of more than 0.5 division in Y
direction, as a result of different attenuator settings in the
range from 5mV/div to 5V/div when the input is not grounded
but screened.
2. TRIGGER-AMP (trigger amplifier)
Compensates higher deviations of the trigger point (symbol)
caused by switch over between AC and DC trigger coupling in
condition internal triggering (Source: CH I or CH II), when a 50
kHz sine wave signal without DC content (AC input coupling
recommended) is applied.
The instrument automatically adjusts and stores the
adjustment values in a non volatile memory after calling the
item. A new adjustment may be necessary after the
temperature conditions have changed once again drastically.
RS232 Interface - Remote Control
Safety
Caution:
All terminals of the RS232 interface are galvanically
connected with the oscilloscope and subsequently
with protective (safety) earth potential.
Measurement on a high level reference potential is not
permitted and endangers operator, oscilloscope, interface
and peripheral devices. In case of disregard of the safety
warnings contained in this manual, HAMEG refuses any
liability regarding personal injury and/or damage of equip-
ment.
Operation
The oscilloscope is supplied with a serial interface for control
purposes. The interface connector (9 pole D- SUB female) is
located on the rear of the instrument. Via this bidirectional
port, the instrument parameter settings can be transmitted
to, or received from a PC.
The maximum connecting cable length must be less then 3
meters and must contain 9 screened lines connected 1:1. The
pin connection of the oscilloscope RS232 interface (9 pole D-
SUB female) is determined as follows:
Pin
2 Tx data (data from oscilloscope to external device)
3 Rx data (data from external device to oscilloscope)
7 CTS (clear to send)
8 RTS (request to send)
5 Ground (reference potential - connected via the oscil-
loscope’s power cord with protective earth)
The maximum voltage swing at pin 2, 3, 7 and
8 is ±12 volt.
The RS232 parameter are:
N-8-2 (no parity bit, 8 data bits, 2 stop bits,
RTS/CTS hardware protocol).
Baud-Rate Setting
After the first POWER UP (switching on of the oscilloscope )
and the first command SPACE CR (20hex, 0Dhex) sent from
the PC, the baud rate is recognized and set automatically
between 110 baud and 115200 baud. The oscilloscope is then
switched over to REMOTE control mode. The oscilloscope
then transmits the RETURNCODE: 0 CR LF to the PC. In this
status all settings (with the exception of those functions
mentioned under “Controls and Readout”) can be controlled
via the interface only.
The only ways to quit this status are:
• Switching the oscilloscope off,
transmitting the command
• RM= 0 from the PC to the oscilloscope, or
• depressing the AUTO SET ( LOCAL ) pushbutton,
if in unlocked condition (command LK=1... was not sent)
After the remote state has been switched off the RM -LED (3)
is dark.
Please note:
A minimum time must elapse between the commands
RM=1... (remote on) and RM=0... (remote off) and vice
versa. The time can be calculated with the formula:
tmin = 2x(1/baud rate) + 60µs.
If at the beginning no SPACE CR command is recognizable,
the oscilloscope pulls the TxD line low for approx. 0.2ms and
causes a break on the PC.
Data Communication
After successfully being set to remote control mode, the
oscilloscope is prepared for command reception.