U8531401-230 [1001022]
3B SCIENTIFIC® PHYSICS
Measurement Amplifier @115 V 1001021
Measurement Amplifier @230 V 1001022
Instruction sheet
06/15 SP/ALF
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the first time, confirm that the specifications
printed on the rear side of the housing are
compatible with the local mains voltage.
1. . Safety instructions
The measurement amplifier conforms to all safety
regulations for electrical measuring, control, monitoring and laboratory equipment, as specified under
DIN EN 61010, Section 1, and the equipment has
been designed to meet protection class I. It is intended for operation in a dry environment, suitable for the
operation of electrical equipment and systems.
Safe operation of the equipment is guaranteed,
provided it is used correctly. However, there is no
guarantee of safety if the equipment is used in an
improper or careless manner.
If it may be assumed for any reason that nonhazardous operation will not be possible (e.g. visible
damage), the equipment should be switched off immediately and secured against any unintended use.
In schools and other educational institutions, the
operation of the AC/DC power supply unit must be
supervised by qualified personnel.

Mains switch
Voltage output +15 V
Voltage output reference
point
Voltage output -15 V
Voltmeter terminals
Polarity reversal switch
Offset calibration knob
Range switch
Current/charge input, BNC
Voltage input, BNC
Ground terminal
“Discharge” button
Before using the AC/DC power supply unit for
1

Before using the AC/DC power supply unit for
the first time, check the housing and the mains
lead for any damage. In the event of any malfunction/operational defect or visible damage,
switch off the unit immediately and secure it
against unintended use.

The instrument may only be connected to the
mains via a socket that has an earth connection.

Before making any connections, check the
experiment leads for damaged insulation and
exposed wires.

Never cover the air vents in the housing. This
is necessary in order to ensure sufficient circulation of air required for cooling the internal
components of the equipment.

The equipment may only be opened/repaired
by qualified and trained personnel.
2. Description
The measuring amplifier can be used for measuring very small voltages, currents and charges.
The design involves a highly sensitive DC amplifier
utilising the modulation principle and featuring silicon varicap diodes. The voltage to be measured is
connected to a bridge composed of varicap diodes
along with a constant high-frequency voltage. The
modulator then outputs a high-frequency signal that
is proportional to the voltage being measured. This
signal is then amplified by a high-frequency amp.
The signal is demodulated by a rectifier that is controlled from the modulation generator by means of
an in-phase control signal. Additional amplifiers
output the signal to terminals for a display instrument. Due to having been inverted twice, the input
and output signals are in phase.
The direct input of the amplifier (terminal “I Q”) can
handle voltages of up to 300 V for a prolonged
period, so that no damage due to overvoltage need
be expected in the course of normal operation.
Caution: voltages in excess of 300 V may only be
applied to terminal “U” (10) with a measuring range
of 100 V/1 V and under no circumstances to terminal “I Q”.
Changes in the measuring range alter the feedback by decades. This also changes the gain factor (and the measuring range) in decade steps.
The input signal may be positive or negative. The
output voltage is in-phase with the measured voltage. A toggle switch (6) can be used to alter the
polarity of the output. For a positive input voltage,
set the switch to the right, for a negative input set it
to the left.
Any DC instrument can be used to display the
results. An output of 1 V to the display instrument
corresponds to the value given by the range setting of the amplifier. Generally instruments with 10
V or 3 V ranges will be used for display purposes.
The limit of the scale thus corresponds to 10 times
or 3 times the number indicated on the front panel
of the amplifier. Display instruments with ranges of
1 V or less should only be used when utmost sensitivity is required (e.g. for 100 V or 10-11 A). Using 10 V or 3 V instruments allows a finer granulation of ranges to be achieved (1 : 0.3). It is not
necessary to adapt the display.
The maximum output to the display is 12 V so that
instruments in the range 10 V/3 V should not be
subjected to damage due to overvoltage. Overloading or short circuits across the output will not
damage the amplifier.
In highly sensitive ranges there may some drifting
of the zero point. This can be corrected using the
“Offset” knob (7). For this terminal “U” (10) must be
connected to the ground terminal (11) (via a conductor or a zero-voltage generator).
The “Discharge” button (12) can be used to short
circuit the amplifier.
The operating voltage of the amplifier is +15 V and
-15 V. This is supplied by a built-in stabilised power supply. The supply voltage can be connected to
external circuitry (e.g. measuring bridges) via the
+15 V and –15 V sockets. They have a common
zero connected to ground. Resistors (10 kilohms)
limit the load capacity of the voltage output (no
short circuit hazard).
The apparatus 1001021 is for operation with a
mains voltage of 115 V (±10%), and the unit
1001022 is for operation with a mains voltage of
230 V (±10%).
3. Technical data
Ranges (with reference to 1 V output voltage):
Voltage:
0.1 mV – 100 V (7 ranges)
Current:
10-11 – 10-5 A (7 ranges)
Charge:
10-11 – 10-7 As (5 ranges)
Input resistance:
Voltage:
10 M
Current/charge:
0 , for voltages up to
300 V
3%
0 – 10 V
Zero point calibration and
reversible polarity
±15 V or 30 V, max. 50 mA
See reverse of apparatus
235 × 230 × 180 mm
2.8 kg approx.
Precision:
Measurement output:
Output voltage:
Operating voltage:
Dimensions:
Weight:
4. Operation
4.1 Voltage measurements
Caution:
Voltages in excess of 300 V may only be applied
to terminal “U” (10) with a measuring range of
100 V/1 V.

Connect voltmeter to terminal pair (5).

Calibrate the zero point for the voltmeter using
the “Offset” knob (7) where necessary (only relevant for highly sensitive ranges).

Connect the voltage to be measured via a
BNC cable to socket “U” (10) and ground (11).

Set the polarity switch (6) to the right for positive voltages or to the left of the measured voltage is negative.
Range
Gain
Value corresponding to scale
limit of display instrument
10 V
3V
1V
100 V
0.01
1000 V
300 V
100 V
10 V
0.1
100 V
30 V
10 V
1V
1
10 V
3V
1V
100 mV
10
1V
300 mV
100 mV
10 mV
100
100 mV
30 mV
10 mV
1 mV
1000
10 mV
3 mV
1 mV
100 V
10000
1 mV
300 V
100 V
4.2 Current measurements

Connect voltmeter to terminal pair (5).

Calibrate the zero point for the voltmeter using
the “Offset” knob (7) where necessary (only relevant for highly sensitive ranges).

Connect the current to be measured via a BNC
cable to socket “I Q” (9) and ground (11).
An output of 1 V to the display from the amplifier
corresponds to the current value selected for the
range.
Measured current = range value on front panel x
deflection of voltmeter.
To output a fixed DC voltage of 30 V:

Connect the positive pole of the load to terminal “L+” (2) and the negative to terminal “L-”
(4).
5. Storage, cleaning and disposal

Keep the equipment in a clean, dry and dustfree place.

Before cleaning the equipment, disconnect it
from its power supply.

Do not clean the unit with volatile solvents or
abrasive cleaners.

Use a soft, damp cloth to clean it.

The packaging should be disposed of at local
recycling points.

Should you need to
dispose of the equipment
itself,
never
throw it away in normal
domestic waste. Local
regulations for the disposal
of
electrical
equipment will apply.
4.3 Charge measurements

Connect voltmeter to terminal pair (5).

Press “Discharge” button (12) to discharge any
existing charge.

Conductors in the circuit may lead to inaccuracies in the measurement (due to innate capacitance, magnetic leakage). For this reason it is
practical to plug a contact pin directly into terminal (9) to measure the charge directly.
The voltage displayed by the voltmeter corresponds to the value of the charge. Here too, an
output of 1 V to the display instrument corresponds
to the charge given by the range setting of the
amplifier.
Since the displayed value for a change is held
static, charges can be applied repeatedly. The
value displayed then corresponds to the sum of all
the individual charges. Any charge applied to the
measuring amplifier can be cancelled out by another charge of opposing sign.
4.4 Use of the measuring amplifier as a DC
power supply
To output a fixed DC voltage of 15 V:

Connect the positive pole of the load to either
terminal “L+” or “L-” (2 or 4). Connect the negative pole to terminal “0” (3).
3B Scientific GmbH ▪ Rudorffweg 8 ▪ 21031 Hamburg ▪ Germany ▪ www.3bscientific.com
Technical amendments are possible
© Copyright 2015 3B Scientific GmbH
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