The TDR-5000 is developed for the measurement of the Dielectric Constant of fluids or bulk goods. A two inch parallel wire sensor picks up the measure value. It is connected to the main unit via a 2 meters BNC coaxial cable. The measure result is available in nearly real time. So it is possible to observe and automatically regulate dynamic processes. Unlike gauges with capacitive measuring the TDR-5000 also can handle middle-grade conductive (up to 1mS/cm) materials. For example, measurements lead to the same results with distilled water (isolating) or with mineral water (conductive).


Functional Description:

The TDR (Time Domain Reflection) principle is dependent upon a time measurement. The TDR-5000 periodically sends voltage pulses with very short rise times (250 ps) onto the sensor cable. Let us have a look at one single pulse`s way: The pulse runs along the coaxial cable up to the point t1, that's the connection point of the parallel wire sensor. At this point the electrical impedance of the conductance changes, therefor a part of the impulse's energy is reflected and runs back on the cable. The rest of energy runs towards the end of the sensor wires (point t2), where another part of the energy is reflected, running back to the source (TDR-5000). There a special sampling circuit analyses the time delay of the partly reflected pulse energy, eliminating the constant run time of the cable. The found sensor run times are shown on a display and are available as a DC-Voltage value. The paragraph following describes how the dielectric properties of the observed material can be found from the measured sensor run time.

Dielectric Constant K

In free space (K=1) the expansion speed of electromagnetic waves is equal to expansion speed of light. It is decreased with raising Dielectric Number K. For poor loss, non magnetic materials there is approximately:

v = Electromagnetic expansion speed, c = light expansion speed, K = Dielectric Constant of the medium the expansion is happening in. By TDR-5000 displayed run time t across the sensor (t = t2 - t1), put into the following relation leads to the value of K:

l = length of the sensor sticks.


Length of sensor l = 5 cm, t = 3 ns measured. Result: K = 81 (water).

Calibrating of Range:


1. Method:

2. Method:


The sensor rods need to be dipped completely.



Sensors for your special utilization could easily be made by yourself or by us:

Oilsensor measuring of printer ink different sized handheld sensors simplest sensor type, whole cable length must be 2 meters