450DV2 DSP Lock-In Amplifier

NEW 450DV2 Dual Channel DSP Lock-In Amplifier

Preliminary Data

Model 450DV2 Features

Scitec Instruments Model 450DV2 is a dual phase dual channel DSP lock-in amplifier. It has been designed for computer control and features both Ethernet and RS232 interfaces. All settings can be managed under browser control. State of the art electronics have been used to produce an instrument that is exceptionally versatile and easy to use. The instrument performs all the usual measurements of a dual phase lock-in amplifier, measuring the in-phase and quadrature components, vector magnitude and phase angle.

	Dual Channel Dual phase instrument with 16 channels of demodulation
	Voltage or current input
	Input Gain settings from x1 to x10,000
	Output Gain settings from x0.001 to x1,000,000
	Frequency range from 1 mHz to 200 kHz
	High performance wide bandwidth input gain stage
	16 channels of digital demodulation
	First, second, third and fourth order digital filters with time constants from 1 µs to 500 ks
	Extensive reference options
	Ethernet and RS232 interfaces
	Control selection and adjustment by onscreen menus and sub-menus via web browser
	All outputs are general purpose and fully programmable

Lock-in amplifiers are used to measure the amplitude and phase of small AC signals in the presence of much larger noise levels. They are widely used to recover small optical signals such as those encountered in spectroscopy and studies of fluorescence and luminescence. However, they also have applications in many other fields including electronics and cryogenics where they can be used in component characterisation, bridge networks and to measure the resistance of superconductors.

The output from a lock-in amplifier is a DC voltage proportional to the amplitude of the input signal but with the noise removed. It is also a function of the relative phase difference between the input signal and the associated reference signal. This property allows lock-in amplifiers to be used for measuring the phase properties of the input signal as well.

Scitec Instruments DSP lock-in amplifiers are dual phase instruments. Dual phase lock-in amplifiers have two demodulators which make measurements with a 90° phase separation.

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 maximum dynamic reserve for the Model 450DV2 is 100dB (*), allowing an input signal buried in noise of up to 100,000 times larger to be recovered.

(*) This figure is subject to change

Specifications

Input Signal Channel

The two input signal channels amplify the input signals to a level suitable for digitisation. High performance, low-noise, broad-band amplifiers are used throughout. The input circuitry can accept voltage or current inputs via the front panel signal input BNC.

	Input: voltage or current inputs, via front panel BNC
	Input gain settings: x1, x5, x20, x100, x500, x2000, x10000
	Input Impedance: 10⁸ ohm//50 pF, dc coupled
	Frequency: 1 mHz to 200 kHz
	Maximum Inputs: 1 V rms for measurements, ±3 V before input protection circuitry comes into operation.
	Dynamic Reserve: 100 dB max(*), limited by a maximum signal input noise voltage of 1 V

(*) This figure is subject to change

Demodulator

There are 16 separate demodulator channels each operating in dual phase mode, producing both an in phase and a 90° out of phase result.
The input to each demodulator can be selected from either input, a combination of them both or 1V.
Each demodulator uses a high accuracy, high bandwidth digital demodulator to recover the input signal.
	Laptop not included.

Low Pass Filters

Following demodulation, first, second, third and fourth order low pass filters may be selected.

	Time Constant: 1 µs to 500 ks in 1, 2, 5, 10 steps
	1.5 MHz output update rate

Reference Channel

	Frequency: 1 mHz to 200 kHz
	Input Impedance: 100 KOhm
	Trigger: Zero crossing at 0 V and -0.1 V. TTL/CMOS trigger points at 2 V and 1 V
	Rising or falling edge triggered
	Acquisition Time: 2 cycles
	Each of the 16 demodulators has a separate reference input which is generated using the following:
	± reference_a · I/J ± reference_b · K/L + osc + phase
	I, J, K and L are in the range 1 to 255. osc is the output from an internal oscillator and phase is phase offset. I, K, osc and phase are selectable per demodulator. J and L are the same on all demodulators.
	Example reference signals possible:
	- Reference A
	- Reference B x 2 (2F operation)
	- Reference A x 4 / 5
	- Reference A / 5 + Reference B x 29 / 7
	- 123kHz
	- Reference B x 10 - 456Hz
	- Reference A x 67 / 13 - Reference B x 9 / 5 + 10Hz

Outputs

	4 Analogue Outputs, 2 BNCs on front panel, 2 BNCs on rear panel.
	Variable gain from x1 to x1,000,000.
	±4V full scale output.
	Each output is selectable from many different internal signals including: Inputs, demodulator outputs, low pass filter outputs, R and theta calculations, internal oscillators, constants.

Computer Interfaces

	RS232
	Ethernet
	Command line control of all variables via RS232, telnet and SSH
	Web control of all variables via http interface
	Data and control output in XML format
	Internal processor runs uClinux with full source available

General

	Power: 9 V, 2 A
	Mechanical: 435(W) x 44(H) x 300(D) mm
	Temperature range: 0-50°C
	Warranty: 2 years from date of shipment

Ordering Information

Model 450DV2

Model 450DV2 Lock-in Amplifier: A complete cased DSP dual channel dual phase lock-in amplifier (requires suitable wall mount power supply).

Useful Documents

Model 450DV2 Data Sheet - pdf (154K)