The model 7310 Noise Rejecting Voltmeter is a flexible instrument designed to offer the engineer or scientist the ability to measure signals that are accompanied by unwanted noise or interference.
The unit can best be visualized as a digital filter, implemented using the latest digital signal processing (DSP) techniques, followed by a true rms to DC converter and digital meter. The filter can be configured as a bandpass stage with adjustable center frequency and Q-factor, as a low-pass filter with adjustable cut-off frequency or bypassed for broadband measurements. A separate analog line-frequency rejection filter adds yet further filtering flexibility.
Input signals may be from single-ended or differential voltage, or single-ended current sources. After amplification, but prior to the digital filter, the discrete Fourier transform of the applied signal and noise can be calculated and displayed graphically on screen. This spectral display mode can then be used to adjust the filter controls so that the instrument is only measuring the required signal.
The model 7310 is very easy to use. All instrument controls are adjusted using soft-touch, front panel push-buttons, with the present settings and measured outputs being displayed on the centrally located, cold fluorescent backlit dot-matrix LCD. Numeric outputs are shown in volts or amps rms or in decibels with respect to a preset reference level and maximum and minimum level indicators indicate the highest and lowest amplitudes since the last reset operation. A large-digits display mode is particularly convenient when using the instrument for a single type of test, giving a very easy to read display.
A LabVIEW driver, downloadable from this site, supports all instrument functions.
Capable of measuring signals from DC to 60 kHz, the instrument is ideal for many audio, mechanical, vibrational and electronic measurements.
Measurement Modes
 

Signal Channel
Voltage Inputs
Modes A only, B only or Differential (A-B)
Full-scale Sensitivity Range AC measurement mode: 10 礦 to 1 V rms in a 1-2-5 sequence;
DC measurement mode 1 mV to 1 V in a 1-2-5 sequence
Input Impedance 10 MW // 30 pF
Maximum Safe Input 30 V pk-pk
Voltage Noise 5 nV/?/font> Hz at 1 kHz
CMRR > 100 dB at 1 kHz degrading by 6 dB/octave
Frequency Response AC measurement mode: 300 mHz to 60 kHz
Gain Accuracy 0.2 % typ, 0.6% max.(full bandwidth)
Distortion -90 dB THD (60 dB signal channel gain, 1 kHz
Grounding BNC shields can be grounded or floated via 1 kW to ground
Current Inputs
Full-scale Sensitivity 10 pA to 1 礎 in a 1-2-5 sequence
Input Impedance < 250 W at 1 kHz
Maximum Safe Input 30 V pk-pk
Voltage Noise 130 fA/?/font> Hz at 1 kHz
Frequency Response AC measurement mode: 300 mHz to 60 kHz
Gain Accuracy ?/font> 0.6 % typ
Grounding BNC shields can be grounded or floated via 1 kW to ground
Line Filter
Type Two cascaded analog second-order frequency rejection (notch) stages, set to center frequencies equal to the line frequency (F) and twice the line frequency respectively
Settings F, 2F, F&2F or disabled
Frequency Rejection Each stage gives greater than 34 dB attenuation at ? % of center frequency
Main ADC
Type 18 bit ADC
Sampling Rate 200 kHz
Digital Filter
Type Two cascaded second order digital filter stages giving an overall fourth-order response.
Settings Bandpass, Low-pass or Flat
Controls
Bandpass Center Frequency: 1.000 Hz to 60 kHz;
Q-factor: 2 to 100 in a 1-2-5 sequence
Low-pass -3dB Frequency: 10 Hz to 28 kHz
Flat None
True RMS - DC Converter & Output Processor
Description True RMS algorithm implemented using a DSP running at a 200 kHz sampling rate and managed by a powerful 68000-series host processor
Output Zero Stability Digital Outputs: No zero drift on all settings;
Displays: No zero drift on all settings:
Analog Outputs: < 5 ppm/篊
Output Smoothing Time Constant: 5 ms to 10 s in a 1-2-5 sequence;
Slope: 6 or 12 dB/octave
Offset Auto and Manual offset of up to ?00 % of the full-scale sensitivity range applied prior to the RMS-DC conversion
Auxiliary Inputs
ADC 1 and 2
Maximum Input 0 V
Resolution 1 mV
Accuracy 5 mV at full-scale
Input Impedance 1 MW // 30 pF
Sample Rate ADC 1 only: 40 kHz max;
ADC 1 and 2: 13 kHz max
Trigger Mode Internal, External or burst
Trigger input TTL compatible Outputs
Signal Monitor
Amplitude 0 V FS
Impedance 1 kW
Filter Output
Function Representation of input signal after filtering by digital filter stage
Amplitude ?0 V (100% = ?/font> 5.0 V in bandpass mode)
Update Rate 200 kHz
Output Bandwidth (-3dB) 25 kHz
Output Impedance 1 kW
DC Output
Function OUTPUT, dB OUTPUT, RATIO, LOG RATIO or USER EQUATION
Amplitude ?0 V full scale
Impedance 1 kW
Update Rate 200 Hz
Auxiliary D/A Output 1, 2, 3 & 4
Max Output ?0 V
Resolution 1 mV
Impedance 1 kW
8-bit Digital Output 8 TTL compatible lines that can be independently set high or low to activate external equipment
Power - Low Voltage ?5 V at 100 mA rear panel DIN connector for powering SIGNAL RECOVERY preamplifiers
Data Storage
Data Buffer
Size 32k 16 and 32-bit data points, may be organized as 1?/font> 32k, 2?/font> 16k, 3?/font> 10.6k, 4?/font> 8k, etc.
Max Storage Rate From NRV: up to 800 16-bit values per second;
From ADC1: up to 40,000 16-bit values per second
Interfaces RS232, IEEE-488. A second RS232 port is provided to allow "daisy-chain" connection and control of up to 16 units from a single RS232 computer port.
Power Requirements
Voltage 110/120/220/240 VAC
Frequency 50/60 Hz
Power < 40 VA
Dimensions
Width 350 mm (13.75")
Depth 415 mm (16.5 ")
Height
with feet 105 mm (4.1 ")
without feet 91 mm (3.6 ")
Weight 8.1 kg (18 lbs)
 

噪声抑制电压表7310是用来测量混入噪声或干扰的信号，使用灵活。它被形象地称为数字滤波器实现数字信号处理技术。