Measuring with the appropriate constant current source
The following test instruments are specially designed for four-point resistance measurements and offer different measurement ranges.
Product selection
Polytec offers the RM3000+ for performing four-point measurements. The device provides constant currents between 10 nA and 100 mA and measures voltages from 0.001 mV to 1000 mV.
For sheet resistance measurements, the range is specified from 1 mΩ/2 bis 1 x 108 Ω/2 . Measurements outside this range are possible but with reduced accuracy.
For volume resistivity measurements, the specified range is from 1 mΩ·cm to 1 × 106 Ω·cm. Measurements outside this range are possible but depend on the type of sample, such as whether it is a thin film or a bulk sample.
Unit Selection
The measured values can be displayed on the screen in mV, Ω/, Ω·cm, or Ω. It is possible to enter either the probe spacing or the wafer thickness, so that the Ω·cm values are automatically calculated and displayed.
Interface and Software
The RM3000+ can be connected to a computer via USB or RS-232. The user can operate the device using the keypad, terminal emulation software such as "HyperTerminal", or the free included software.
| Measurement Range | 1 mΩ/2 - 100 MΩ/2, 1 mΩ.cm - 1 MΩ.cm |
|---|---|
| Units | mV, Ω/2, ohm.cm (wafer), ohm.cm (volume), ohms |
| Onboard memory | 50 time-stamped measurements |
| Software | For operation and data control is supplied free of charge |
| Autorange | Determines the appropriate power settings |
| Current | 10 nA - 100 mA. Reversible for contact and measurement verification |
| Accuracy | better than 0.1% against resistors for 100 nA and larger |
| Connections | USB or RS-232 |
| Correction | Possibility of entering a correction factor to adjust the displayed measured values |
| Ohm.cm | Possibility of entering the probe distance or wafer thickness for automatic calculation |
The ResTest is a constant current source and digital voltmeter with a color display. It provides constant currents between 1 μA and 10 mA and measures voltages from 0.04 mV to 4000 mV.
The device has a measurement range from 10 mΩ/² to 1 MΩ/² or 10 mΩ·cm to 10,000 Ω·cm. Measurements outside this range are possible depending on the type of sample, but may reduce accuracy. The measurement values are displayed directly in mV, surface resistance, and volume resistance, and can be saved on the system or on a memory stick.
The HM21 has been designed for performing four-point measurements. The device offers six constant current settings between 100 nA and 10 mA and measures voltages from 0.01 mV to 1250 mV.
For surface resistance measurements, the measurement range is specified from 1 Ω/² to 10 MΩ/². Measurements outside this range are possible but with reduced accuracy.
For volume resistance measurements, the specified range is from 10 mΩ·cm to 10 kΩ·cm. Measurements outside this range are possible, but depend on the sample type, e.g., whether the sample is a thin layer.
Unit Selection
The measurements can be displayed on the screen in mV or Ω/².
Interfaces and Software
The HM21 can be connected to a computer via a USB connection. The user can operate the device using the keyboard, terminal emulation software such as "HyperTerminal", or the included free software.
| Measurement Range | 1 Ω/2 - 10 MΩ/2, 10 mΩ.cm - 10 KΩ.cm |
|---|---|
| Units | mV, Ω/2 |
| Onboard Memory | 50 measurements |
| Onboard Memory | For operation and data control, it is supplied free of charge |
| Current | 100 nA - 10 mA. Reversible for contact and measurement verification |
| Accuracy | 0.5% over the entire range for resistances, better than 0.2% in the middle range |
| Connections | USB |