Model 1294A Impedance Interface

Model 1294 Impedance Interface

Electrical impedance is a well-proven, powerful technique for analyzing the physical and chemical properties of a wide range of materials (see Applications)

Historically, use of the technique with high impedance, low loss materials was limited by a number of factors, such as the ability to measure accurately the very low currents involved, particularly when high electrode impedances are present. The Model 1294 Impedance Interface has been designed specifically to overcome these difficulties, and to meet the present and future needs of materials analysts everywhere.

Used in conjunction with Solartron’s 1260 or 1255 Frequency Response Analyzers, the 1294’s advanced measurement technology offers:

Improved accuracy:

True differential 4-terminal connections minimize the effects of localized disturbances at the current injection points
Balanced generator
Driven shields

Wide measurement range:

1μV, 1pA sensitivity
Impedance range 10^-2 to >10⁹ Ω (>1 GΩ) to cover virtually all materials
Up to 750kHz frequency range

Temperature control:

1294 system interfaces with standard temperature controllers, cryostats and furnaces

Safety compliant:

IEC 601 connections - for in-vivo investigations into a wide range of applications including cosmetics, skin hydration, tissue impedance and tooth decay.

Applications

Civil Engineering:

Cement paste research
Content/strength of concrete mixes

Adhesives:

Epoxy resin curing
Thermoset polymers

Biomaterials:

Ischemia and tumor research
Tooth decay
Dermatological studies
Research in fruit and plants

Ceramics/Composites:

Gas sensors
Gas separation membranes

Impedance measurement
Any material is able to pass current when a voltage is applied to it. If a variable (AC) voltage is applied to the material, the ratio of voltage to current (V/I) is known as the impedance. In many materials the impedance varies with the frequency of the applied voltage, in a way that is related to the physical structure of the material, to chemical processes within it, or to a combination of both.

Accurate measurement of the impedance of materials, by applying a low level signal over a wide frequency range, can yield valuable information about the properties of the material. For example, measuring the impedance of a sample of organic tissue - anything from a piece of fruit to a human kidney - can reveal its condition and suitability for storage, freezing or transplant. Samples of concrete or cement can be analyzed to predict strength, or water/cement/binder mix, and complex curing cycles for composite structures such as aircraft wings can be monitored and controlled.

Impedance is

Non-invasive: impedance can often be measured with surface electrodes.
Non-destructive: low level stimuli required typically have no (or minimal) effect on material being investigated.
Repeatable: many impedance tests compare the state of a material over a period of time, or under varying conditions, e.g. adhesive curing. Consistent measurements are essential for a true indication of these change

Specifications

	PC control connections	to 1294: Parallel interface to FRA: IEEE488 interface
	1294 measurement connections	to FRA: Gen, V1 Hi, V1 Lo, V2 Hi to sample: Normal: 4-terminal connections; IEC601: 4-terminal connections
Generator Output
	Voltage Mode
		Normal connections			IEC601 connections
	Max. DC voltage	±10 V			±10 V*
	Max. AC voltage	7 V rms			7 V rms*
	Max. AC + DC	±10V peak			±10V peak*
	Current Mode
		Normal connections			IEC601 connections
	Transconductance	10 mA/V			10 mA/V*
	Max. DC current	±45 mA			±10 μA*
	Max. AC current	30 mA rms			10 mA rms*
	Max. AC + DC	±45 mA peak			±14 mA peak*
	* subject to IEC601 current limits. Balanced generator capability in voltage mode only.
Generator input (from FRA Gen connector)
	Rear connection	single BNC
	Max. input voltage	10V peak from 50 Ω source
	Switchable attenuator	x1 / x0.01
	Switchable gain	x1 / x2
	Input impedance	50 Ω for x1, 25 kΩ for x2
Voltage buffers
	Driven shield connections to sample
	Amplifier gain	x1
	Common mode range	±10 V
	Bias current	1 nA max
	Input resistance, to ground	>1 GΩ
	Input capacitance	10 pF to ground
	Input capacitance	1 pF (differential)
Voltage buffer output (to FRA V1Hi & V1Lo)
	Rear connections	two BNCs
	Maximum output	±10 Vpeak
	Output resistance	50 Ω
Current to voltage converter
	Rear panel Selector	Current Range	Resolution			FRA Range		Range Resistor
	1 V/100 mA	30 mA		1 µA		300 mV	10 Ω
	1 V/100 mA	3 mA		100 nA		30 mV	10 Ω
	1 V/10 mA	300 µA		10 nA		30 mV	100 Ω
	1 V/1 mA	30 µA		1 nA		30 mV	1 kΩ
	1 V/100 µA	3 µA		100 pA		30 mV	10 kΩ
	1 V/10 µA	300 nA		10 pA		30 mV	100 kΩ
	1 V/1 µA	30 nA		1 pA		30 mV	1 MΩ
Current to voltage converter output (to FRA V2 Hi)
	Rear connection	single BNC
	Maximum output	300 mV rms
	Output resistance	50 Ω
PC Software Provides control of FRA, 1294 and optional temperature controller.
	Result parameters	Z, Y, E, M, C*
	Result formats	real, imaginary, magnitude,phase, tanδ
	plotted vs:	frequency, time, temperature, bias, AC level
	plotted on:	Bode, complex plane
General
	Power supply	90 VAC to 264 VAC, (47Hz to 440Hz)
	Power consumption	18 W
	Weight	14.5 lb (6.5 kg)
	Operating temperature	5° to 40°C (40° to 104°F)
	General safety	EN61010
	Medical safety	IEC601, EN60601-1 (Power supply: 47 to 65 Hz)
Medical safety		Passive circuits in the drive and sense lines of the IEC601 connections protect live subjects from excess current in accordance with the IEC601 standard.
	: : 1294 Typical measurement accuracy 4-terminal measurements assume simulated electrode impedance of 10x sample impedance.

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