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 (for example In-Vivo measurements). The 1294A 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 1260A or 1255A Frequency Response Analyzers, the 1294A’s advanced measurement technology offers:
Wide measurement range:
- True differential 4-terminal connections minimize the effects of localized disturbances at the current injection points
- Balanced generator
- Driven shields
- 1 μV, 1 pA sensitivity
- Impedance range 10 mΩ to >1 GΩ to cover a wide range of materials
- Up to 750 kHz frequency range
- 1294A system interfaces with standard temperature controllers, cryostats and furnaces
- IEC 601 connections - for In-Vivo investigations into a wide range of applications including cosmetics, skin hydration, tissue impedance and tooth decay.
|Cement paste research
||Ischemia and tumor research
|Content/strength of concrete mixes
||Research in fruit and plants
|Epoxy resin curing
||Gas separation membranes
All materials are able to pass current when a voltage is applied. 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.
- 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