spacer.gif (918 bytes) Clarke-Hess Comjmunication Research Corp.

Multi-function Gain-Phase Analyzer
(Frequency Response Analyzer)
Model 2505

Model 2505 Gain Phase Analyzer
Standard Configurations
Gain phase analyzer
Frequency response analyzer
Phase Angle Voltmeter (PAV)
Fast dual channel wide-band voltmeter
Phase meter
Complex impedance bridge
Spectrum / Harmonic analyzer
Wide-band power analyzer
Dual channel sampling oscilloscope

Isolated / floating inputs, dc-2MHz
Auto rejection of noise and harmonics
Internal Function Generator
0.1mV to 500V range
Alarm on any measurement
RS232 and printer port, IEEE-488 option

High resolution vacuum fluorescent

Outputs presented as tables or graphs
Magnification for large clear results
Typical applications
Testing of closed loop feedback systems
Synchro, resolver, RVDT and LVDT test
Inductor / transformer testing
Incoming inspection of components
Complex impedance measurement
Core loss measurements
Ultrasonic power measurements
Power line carrier signal measurements
Multi-function testing in University labs


The Model 2505 is a multi-function instrument which is ideal for users that must make a large variety of sophisticated measurements. A single package, contains a Gain Phase Analyzer (Frequency Response Analyzer),  Phase Angle Voltmeter with a null detector, Function Generator,  Pulse Generator,  Spectrum Analyzer,  Digital Sampling Oscilloscope,   Wattmeter,  Phase Meter and  Complex Impedance Bridge. These internal instruments cover the frequency range from dc (10mHz for the ac instruments) to more than 2MHz.

Each of these internal instruments may be used independently or in an internally correlated fashion. By selecting the internal Function Generator and the two Voltmeters, the user can obtain dual gain-phase data for two outputs of any network he is testing. This is particularly useful for making Bode plots to check the stability of networks having feedback. These plots can be displayed in several formats using the oscilloscope capability of the Model 2505. Because of the floating inputs, the measurements can be made across network components with neither side connected to ground.

In its Phase Angle Voltmeter (PAV) mode, the Model 2505 presents, on a single display, the total rms, the in-phase and quadrature components, the phase angle and the fundamental magnitude. An additional display provides the ratios of the various parameters.  An internal null meter provides the user with the ability to make precision ratio adjustments.  The specifications in this mode are superior to the specifications of all competing PAVs regardless of their cost. In addition, unlike traditional PAVs, the Model 2505 has the advantage of a built-in signal generator. All of these features make the Model 2505 ideal for synchro, resolver, RVDT and LVDT testing.

The Spectrum Analyzer feature can be used to observe the harmonic content of complex, periodic input signals. This proves to be especially useful for examining current waveforms to ensure that they do not exceed the requirements placed on harmonics.

As a true rms Wattmeter, the Model 2505 is ideally suited to measure core loss, input power to ultrasonic transducers, power consumed by switching power supplies, and many other devices operating at higher frequencies. It also performs exceptionally well with measurements at 50Hz or 60Hz.

The Complex Impedance Bridge function permits the user to measure Resistance, Inductance and Capacitance at frequencies from dc (Resistance only) to 2MHz. Secondary functions such as Q (quality factor), D (dissipation factor), and ESR (equivalent series resistance) can also be measured over the same frequency range.

Data are presented on an orange, vacuum luminescent display either in tabular form or in a swept graphical form, e.g., an amplitude vs. frequency plot for a linear network. The tabular form comprises a list of the frequencies with their corresponding amplitudes. A zoom function permits the user to enlarge items of interest on the display.

Typical Displays

Voltmeter (Magnified)


Gain vs. Frequency
Gain vs. Frequency

Sensitive Level Meter
Selective Level Meter
Spectrum Analyzer
Spectrum Analyzer
Power Meter
Power Meter
Gain Phase Amalyzer
Gain Phase Meter
Impedance Bridge
Impedance Bridge
Transformer Analyzer
Transformer Analyzer


CH1 & CH2 Voltmeters
Channels / display 2 isolated / 5 digits
Measurement Rms, ac, dc, peak, cf, surge
Frequency Dc to 2MHz
Coupling Ac or ac+dc
Max input ▒500V peak
▒500V peak from earth
Input ranges 500V 300V, 100V, 30V, 10V, 3V, 1V, 300mV, 100mV, 30mV,10 mV
Ranging control Full auto, up only, or manual
Input impedance 1 M // 30pF (excluding. Leads)
Accuracy (ac)
All + 0.4mV
0.1 % range < 1 kHz
0.3% range < 10kHz
1 % range < 50kHz  + 0.004% rdg per  kHz to 2MHz
Accuracy (dc) 0.2% range + 2mV
CMRR >55dB @ 10V 1 MHz
>110dB @ 100V 1 kHz
Time constant 0.2s, 1.5s or 12s

Phase Meter
Frequency 10mHz to 2MHz*
Measurement DFT analysis
Phase accuracy 0.02░ < 100Hz 0.05░ < 1 kHz
0.25░ < 10kHz + 0.005░ per kHz

Gain phase analyzer (Frequency response analyzer)
Frequency range 10mHz to 2MHz*
Modes Gain, angle, real, imaginary
Accuracy ▒0.02dB

LCR meter
Frequency range 10mHz to 2MHz*
Measurement DFT analysis
Functions L, C, R (ac), R (dc), Z, Q, tan­, ě, series or parallel
Ranges 10pF to 1F
100nH to 1000H
100mW to 10MW
Accuracy 0.3% < 1 kHz, 0.75% < 10kHz 2.5% < 50kHz, 12.5% < 1 MHz

Transformer analyzer
Inductance L 100nH to 1000H Series / Parallel
Quality factor Q 0.001 to 2000
Leakage inductance 100nH to 1000H
Inductance match 1:5000 to 5000:1
Turns ratio (voltage) 1:70000 to 70000:1
Turns ratio (Inductance) 1:2000 to 2000:1
Winding polarity / phasing Pass/fail or  ▒indication
Dc R & winding continuity 20mW to 100kW
Inter winding phase angle 0░ to 360░ or ▒180░
Impedance test 10mW to 100MW
Insertion / return loss -100dB to 100dB
Frequency response 10Hz to 2MHz
Longitudinal balance 0dB to 100dB
Inter winding capacitance 10pF to 1F
Inter winding capacitance match 1:5000 to 5000:1
Distortion THD 0.1 % to 100%

Signal generator
Waveforms sine, triangle, square, sawtooth, dc only
Frequency 10mHz to 2.4MHz (sine); 10mHz to 1MHz (other)
Accuracy Frequency ▒0.05%; Amplitude ▒5% +5mVrms
(to 100kHz)
Output impedance 50W
Output voltage 10mV to 10V peak
Offset 0V to 10V

Pulse generator
Frequency 10mHz to 2.4MHz
Pulse width 200ns to 10s (50ns resolution)
Rise and fall time selectable 50ns (5V) to 1s

Phase Angle Voltmeter PAV (Vector Voltmeter)
Measurement Total rms, in-phase and quadrature components, phase angle, fundamental magnitude, and ratio with null meter capability.
Range 10mHz to 1MHz
Accuracy See voltmeter/phase meter specifications

Low frequency DSO / waveform display
Channels 2
Time-base 20us to 5s per division
Roll mode Time-base >1s/div
Pretrigger None, 25%, 50%, 75%
Sample rate 800k sample/sec

Power meter
Measurements W, VA, power factor, V, A total, fundamental, integrated
Current and Voltage accuracy ▒0.1 % reading
Power accuracy (power factor >0.7) ▒(0.3% rng + 0.3% rdg), f < 1kHz;
▒(0.7% mg +0.3% rdg), f < 10kHz;
▒(2% mg +0.5% rdg), f < 50kHz;
▒(2% rng + 5% rdg), f < 1MHz

Selective level meter
Frequency range 10Hz to 2MHz
Scan single, dual, or sweep
Selectivity (-3dB) 3Hz, 24Hz, or 100Hz

Display 160 x 80 dot graphic electroluminescent
Size Approximately 48.3 (Rack Mountable) x 15 x 25 cm  
Temperature range Operating: 0░ to 40░C
Within specification: 23░ ▒5░C
Weight Approximately 5kg
Power supply 115 V rms ▒10%, 60Hz, 30VA max.
Warranty 1 year

Ordering information
Model number 2505  Approximately 19" W (Rack Mountable) x 3.5" H x 13” D

Input probes, BNC output cable, RS232, RS232 cable; power cord, manual, Certificate of Calibration

Option IEEE IEEE-488 interface
Option 01-A Active LCR Test Head Includes Kelvin clips
Option 01-P Passive LCR Test Head Includes Kelvin clips
Option 03A Injection transformer (for gain-phase measurements)
Option 04 Amplifier, 20Vp-p at 1 A

*20mHz to 1 MHz if not using generator


3243 Route 112, Medford, NY  11763
Phone: (631) 698-3350   Fax: (631) 698-3356