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 Features
 Scitec Instruments Model 420 is a dual phase analogue
lock-in amplifier. Both the single phase Model 410 and dual
phase Model 420 are suitable for making amplitude and phase measurements but it
is significantly easier with the Model 420.
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Dual phase instrument |
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Differential or single-ended input |
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Gain settings from 3 µV to 1 V |
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10 Hz to 100 kHz |
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High performance wide bandwidth input gain stage |
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Analogue meter for display of output signals |
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Output offset controls |
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Output time constants from 100 µs to 30 s |
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1F and 2F reference signal operation |
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90° step and fine phase control |
Scitec Instruments lock-in amplifiers are available as
both single phase and dual phase instruments. Single phase lock-in amplifiers
have a single demodulator and can be used to make both amplitude and phase
measurements. However a manual set-up procedure is required both initially and
following any phase change of the output signal. Dual phase lock-in amplifiers
have two demodulators which operate with a 90° phase separation. In-phase
and out-of-phase components are measured simultaneously which simplifies the
process of making amplitude and phase measurements. In addition the Model 420
has circuitry for calculating the vector magnitude from the output of the two
demodulators. The Model 420 instruments can be used to make measurements of the
input signal at both the first and second harmonic of the reference signal.
A key figure of merit used for lock-in amplifiers is
dynamic reserve. The dynamic reserve of a lock-in amplifier is defined as the
ratio of the noise to signal that is allowed before saturation occurs. The
dynamic reserve for the Model 420 is 60dB, allowing an input signal buried in
noise 1000 times larger to be recovered. |
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Specifications
Input Signal Channel
The input signal channel amplifies the input signal to a level
suitable for the demodulator. High performance, low-noise, broad-band
amplifiers are used throughout. The input circuitry can accept a differential
or single-ended input via the front panel signal input BNC.
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Input: High or low impedance differential or single ended
via front panel BNC |
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Sensitivity: 3 µV to 1 V (for 1 V output) switched in
1, 3, 10 steps |
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Input Impedance: 10¹²W//1 nF, dc coupled |
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Frequency: 10 Hz to 100 kHz |
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Maximum Inputs: ±16 V before input protection
circuitry comes into operation. The input BNC has been tested for electrostatic
discharge damage |
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Input Noise Voltage: Other lock-in amplifier manufacturers
give input noise values but without providing any definition of this
specification. Indeed there is no meaningful definition of this specification
in relation to lock-in amplifiers. As such, Scitec Instruments does not provide
noise values and other manufacturers data sheets are considered misleading.
Further details about input noise are available on request |
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Gain Accuracy: 1% |
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Gain Stability: 200 ppm/°C |
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Dynamic Reserve: 60 dB limited by a maximum signal input
noise voltage of 10 V |
Demodulator
The output of the signal input stage is processed using two very
high bandwidth demodulators each operating 90° apart from each other to
produce the X and Y signals.
Low Pass Filter
The X and Y outputs from the demodulators are passed through two
first order low pass filters and then amplified. The X and Y signals are
combined to produce R, the modulus signal, where
R=(X2+Y2)1/2 before output via a front panel
BNC.
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Time Constant: 100 µs to 30 s in 1, 3, 10
steps |
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All Outputs: +/-1 V output corresponds to full scale input.
Short circuit protection included. |
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Front Panel Output: X, Y or R switchable output |
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Rear Panel Outputs: X, Y and R separate outputs |
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Offset: Up to 1x full scale for both X and Y channels,
switchable on or off |
Reference Channel
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Frequency: 10 Hz to 100 kHz |
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Input Impedance: 5.6 M ac coupled |
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Trigger: Sine - 100 mV rms min (15 V max.) Pulse - 5 V, mark
to space ratio in the range 20:1 to 1:20. |
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Acquisition Time: 10 s max. |
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Phase Control: 90° steps + fine shift in range 0° -
100° |
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Phase Drift: 0.1°/°C |
General
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Power: 115 Vac, 230 Vac; 50-60 Hz; 10 VA max. |
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Mechanical: 440(W) x 87(H) x 190(D) mm |
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Temperature range: 0-50°C |
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Warranty: 2 years from date of shipment |
Standards
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Electrostatic Discharge: BS EN 61000-4-2 Level 2 |
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Surge: BS EN 61000-4-5 Level 3 |
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Burst & Transient: BS EN 61000-4-4 Level 2 |
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RF Emissions: BS EN 50081-2 |
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RF Immunity: BS EN 61000-4-3 / BS EN 50082-2 |
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Low Voltage Directive: BS EN 61010-1 |
Please contact us for
additional information. |
