Modulation Inputs; Tracking; Safety Features; Cooling - Hameg Instruments Hm8142 Handbuch

O p e r a t i n g m o d e s

Tracking

With the aid of the tracking function, it is possible to simultaneously
vary 2 setting parameters. In other words, either both output volta-
ge settings or both current limits can be varied at the same time by
using the tracking function. This function is activated by pressing
the TRACKING button . The TRACKING LED is lit. To exit the
tracking mode, press the TRACKING button
This has the effect of clearing all previously activated functions,
and from then on whenever a value is called and changed both
channels of the instrument are identically affected (the 5 V out-
put remains unchanged). It doesn't matter which values had
been set prior to changing one of the parameters; in the tracking
mode, the HM8142 always retains the respective differences
between the voltages values and the current limits. When the
maximum permissible level is reached by the larger value, its
lower counterpart cannot be increased further.
For instance, if one channel of the power supply is set to 22 V
and the other to 10 V, the greatest possible output voltages that
can be programmed in tracking mode are 30 V and 18 V, re-
spectively. The same applies analogously to the programmed
current limit values.

Safety features

The HM8142 is equipped with a variety of safety features to pre-
vent damage being caused to the instrument by short circuits or
overheating. If one of the output voltages is short circuited, the
current limiter automatically keeps the current from rising bey-
ond the programmed maximum output current. The response
time is approx. 200 μs. If the output current should exceed the
programmed limit during the response time, then a second
current limitation feature takes effect after a delay time of 2 μs,
preventing the current from exceeding a level of 3 A.

Cooling

The heat generated in the HM8142 is removed by a temperature
controlled fan. This is located together with the heat sink in a
"cooling channel" that runs straight through the instrument.
Air is drawn in on the righthand side of the unit and blown out
again on the lefthand side. This also prevents excessive dust
accumulation.
Always make sure that there is suffi cient open space for coo-
ling on both sides of the HM8142. In no case may the cooling
holes on the sides of the unit be covered.
If the temperature inside the HM8142 should nevertheless
rise to above 80 °C, an automatic temperature-controlled safety
circuit is activated. The outputs are put off and the REMOTE LED
on the front panel fl ashes. The message U1 appears in the
display. After the unit has cooled down suffi ciently, operation can
be resumed by pressing the LOCAL button
outputs by pressing the OUTPUT button

Error messages

When malfunctions occur during operation of the HM8142 in its
normal modes, error messages are displayed on the instru-
ment. The possible error states are as follows:
HM 8142 Meaning
U1 Templim Overheated
U2 RAMERR Zeropower RAM is defective
U3 Bad IEC! Ilegal IEC address
U4 Checksum EPROM defective
22
Subject to change without notice
All manuals and user guides at all-guides.com
U5
U6
*) Also displayed if an input voltage greater than 3 V is applied
If any of these error conditions occur, the outputs are disabled
and a sweeping light appears in the displays in addition to the
again . error message. In case of errors 2 or 4 the instrument has to
be sent in for repair. The other error messages can be reset
by pressing the LOCAL button
has been eliminated, normal operation can be resumed by
activating the outputs.

General

For the HM8142 a RS-232, IEEE-488 or USB interface is avai-
lable. We recommend the installation ex factory.
Interface parameters: 4800 baud, 8 N 1, XON/XOFF
When being controlled by interface, the HM8142 immediately
goes into remote mode as soon as a command arrives at the
interface. Mixed operation, in which the instrument can also
be manually operated using the frontpanel controls although
it is connected to an interface, is possible by using the com-
mand MX1.
If the wait times set in the controller are too short, this can
lead to timeout errors. The commands have to be terminated
with CR (0x0D). The commands may contain upper and lower
case characters.

Description of commands

RM1/RM0
Format:
Function: Puts the power supply in remote mode.
The frontpanel controls are disabled. In this mode, the power
supply can only be operated by interface. This mode can be
terminated by sending a RM0 command or pressing the LO-
CAL button.
Format:
Function: Disables the remote mode, returning the power sup-
ply to local mode (permitting operation using the front panel
controls). The RM0 command also has the effect of counter-
acting the LK1 command.
and activating the MX1/MX0
. Format:
Function: Switches the power supply from remote mode into
mixed mode. In mixed mode, the instrument can be operated
either by interface or using the frontpanel controls.
Format:
Function: Terminates mixed mode and returns the instrument
to remote mode.
LK1 / LK0
Format:
Function: Switches the HM8142 to localinhibit mode. The LO-
CAL button is disabled. The power supply can now only be ope-
Over-V! Measured voltage ≥ 31 V*
Over-I! Measured current ≥ 1.1 A
to one of the modulation inputs.

Remote control

RM1
RM0
MX1
MX0
LK1
. Once the error condition