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The Laureate Ohmmeter is ideal for high-speed, high-accuracy resistance measurements in a production environment, such as contact resistance measurements. It is factory calibrated for five jumper selectable resistance ranges from 20.000 ohm to 200.00 kohm. Fixed, factory-special ranges of 2.0000 ohm, 2.0000 Mohm and 20.000 Mohm are also available. Accuracy is an exceptional ±0.01% of reading ± 2 counts. Resolution is one part in 20,000. In the 2 ohm range, resolution is 0.1 milliohm, making the meter suitable for contact resistance measurements.
An Extended ohmmeter version is ideal for use with nonlinear sensors whose output is a changing non-linear resistance. Extremely accurate custom curve linearization is provided by curvilinear spline fits, and the reading can be scaled in software to read in user-selected engineering units of measure.
Meter connections can be via 2, 3 or 4 wires. With 4-wire hookup, 2 wires are used for excitation and two separate wires are used to sense the voltage across the resistance to be measured, thereby eliminating any lead resistance effects. With 3-wire hookup, the meter senses the combined voltage drop across the resistance to be measured plus two excitation leads. It also senses the voltage drop across one excitation lead, and then subtracts twice this voltage from the combined total. This technique effectively subtracts lead resistance if the excitation leads are the same.
All resistance ranges are digitally calibrated at the factory, with calibration factors stored in EEPROM on the signal conditioner board. This allows ranges and signal conditioner boards to be changed in the field without recalibrating the meter. If desired, the meter can easily be calibrated using external standards plus scale and offset in software.
High read rates at up to 60 or 50 conversions per second while integrating the signal over a full power cycle are provided by Concurrent Slope (US Pat 5,262,780) analog-to-digital conversion. High read rates are ideal for high-throughput manufacturing processes. Peak and valley values are automatically captured and may be displayed via a front panel pushbutton command or a control signal at the rear connector, or be transmitted as serial data.
Designed for system use. Optional plug-in boards for communications and control include Ethernet, WiFi and serial communication boards, dual or quad relay boards, and an isolated analog output board. Laureates may be powered from 85-264 Vac or optionally from 12-32 Vac or 10-48 Vdc. The display is available with red or green LEDs. The 1/8 DIN case meets NEMA 4X (IP65) specifications from the front when panel mounted. Any setup functions and front panel keys can be locked out for simplified usage and security. A built-in isolated 5, 10, or 24 Vdc excitation supply can power transducers and eliminate the need for an external power supply. All power and signal connections are via UL / VDE / CSA rated screw clamp plugs.
Multiple relay operating modes are selectable in software. One of these is band deviation setpoint operation, where a deviation limit (such as 50 counts) is set up around both sides of the setpoint. The relay closes (or opens) when the reading falls within the deviation band, and opens (or closes) when the reading falls outside of this band. This mode sets up a passband around the setpoint and is often used for component testing.
| Ohmmeter hookup can be via 2, 3 or 4 wires to the J5 connector. The meter applies a fixed excitation current for each resistance range. | |
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In 4-wire hookup, different pairs of leads are used to apply the excitation current and sense the voltage drop across the unknown resistance, so that the IR drop across the excitation leads is not a factor. |
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In 3-wire hookup, the meter senses the combined voltage drop across the unknown resistance plus two excitation leads. It also senses the voltage drop across one excitation lead, and then subtracts twice this voltage from the combined total. This technique effectively subtracts all lead resistance and compensates for ambient temperature changes if the two excitation leads are identical. |
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In 2-wire hookup,the meter senses the combined voltage drop across the unknown resistance and both lead wires. The voltage drop across the lead wires can be measured by shorting out the resistance during meter setup, and this voltage is then automatically subtracted from the combined total. However, changing resistance of the lead wires due to ambient temperature changes will not be compensated. |
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A deviation limit (50 mohm in this example) is set up around both sides of a setpoint. The relay closes (or opens) when the reading falls within the deviation band, and opens (or closes) when the reading falls outside of this band. This mode sets up a passband around the setpoint and can be used for contact resistance testing.
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| Range | Ohms | Resolution | Accuracy | Excitation Current *** |
|---|---|---|---|---|
| R0** | 0-2.0000 Ω | 0.1 mΩ | ±0.01% of reading ± 2 counts |
5 mA |
| R1* | 0-20.000 Ω | 1 mΩ | 5 mA | |
| R2* | 0-200.00 Ω | 10 mΩ | 500 µA | |
| R3* | 0-2000.0 Ω | 100 mΩ | 50 µA | |
| R4* | 0-20000 Ω | 1 Ω | 5 µA | |
| R5* | 0-200.00 kΩ | 10 Ω | 500 nA | |
| R6** | 0-2.0000 MΩ | 100 Ω | 500 nA | |
| R7** | 0-20.0000 MΩ | 1000 Ω | 80 nA |
| * Jumper-selectable, precalibrated range. |
| ** Factory-set fixed range. |
| *** The applied excitation current is sensed by the meter, which operates in a ratiometric mode and automatically compensates for any changes in excitation. |
| Display | |
|---|---|
| Readout | 5 LED digits, 7-segment, 14.2 mm (.56") |
| Color | Red or green LED |
| Indicators | 2 red LED lamps |
| Accuracy | |
| Accuracy at 25°C | ±0.01% of reading ± 2 counts |
| Span tempco | ±0.003% of reading/°C |
| Electrical | |
| Connection | 2, 3 or 4-wire |
| Max applied voltage | 100 mV |
| Overvoltage protection | 125 Vac |
| Open sensor indication | Flashes full-scale |
| A-to-D Conversion | |
| Technique | Concurrent Slope (Pat 5,262,780) |
| A-to-D rate | 60/s at 60 Hz, 50/s at 50 Hz |
| Output update rate | 56/s at 60 Hz, 47/s at 50 Hz |
| Display update rate | 3.5/s at 60 Hz, 3/s at 50 Hz |
| Power Supply Boards (one required) | |
| Voltage, standard | 85-264 Vac or 90-300 Vdc |
| Voltage, optional | 12-32 Vac or 10-48 Vdc |
| Frequency | DC or 47-63 Hz |
| Power consumption (typical, base meter) | 1.2W @ 120 Vac, 1.5W @ 240 Vac, 1.3W @ 10 Vdc, 1.4W @ 20 Vdc, 1.55W @ 30 Vdc, 1.8W @ 40 Vdc, 2.15W @ 48 Vdc |
| Power Isolation | 250V rms working, 2.3 kV rms per 1 min test |
| Analog Output Board (one optional) | |
| Output levels | 4-20 mA, 0-20 mA, 0-10V, -10 to +10V (jumper selectable) |
| Current compliance | 2 mA at 10V ( > 5 kΩ load) |
| Voltage compliance | 12V at 20 mA (< 600 Ω load) |
| Scaling | Zero and full scale adjustable from -99999 to +99999 |
| Resolution | 16 bits (0.0015% of full scale) |
| Step function response | 80 ms to 99% of final value (typ) |
| Isolation | 250V rms working, 2.3 kV rms per 1 min test |
| Relay Output Boards (one optional) | |
| Dual magnetic relays | 2 Form C, 8A at 250 Vac or 24 Vdc, 0.3A at 250 Vdc, resistive load |
| Quad magnetic relays | 4 Form A (NO), 8A at 250 Vac or 24 Vdc, 0.3A at 250 Vdc, resistive load |
| Dual solid state relays | 2 Form A (NO), 120 mA at 140 Vac or 180 Vdc, resistive load |
| Quad solid state relays | 4 Form A (NO), 120 mA at 140 Vac or 180 Vdc, resistive load |
| Relay commons | Isolated commons for dual relays or each pair of quad relays |
| Relay isolation | 250V rms working, 2.3 kV rms per 1 minute test |
| Step function response | 30 ms (typ) for contact relays, 25 ms (typ) for solid state relays |
| Relay latching modes | Latching or non-latching |
| Relay active modes | Active on or off, active high or low |
| Hysteresis modes | QA passband mode, split hysteresis, span hysteresis |
| Communication Boards (one optional) | |
| Board selections | RS232, RS485 with dual RJ11 connectors, RS485 with dual RJ45 connectors, USB, Ethernet, USB-to-RS485 gateway, Ethernet-to-RS485 gateway, WiFi with built-in antenna plus USB & RS485, WiFi with external antenna plus USB & RS485 |
| Protocols | Laurel Custom ASCII (serial), Modbus RTU (serial), Modbus TCP (Ethernet or WiFi) |
| Digital addresses | 247 (Modbus), 31 (Laurel ASCII), |
| Isolation | 250V rms working, 2.3 kV rms per 1 min test |
| Environmental | |
| Operating temperature | 0°C to 55°C standard, -40°C to 70°C with -X option |
| Storage temperature. | -40°C to 85°C |
| Relative humidity | 95% at 40°C, non-condensing |
| Protection | NEMA-4X (IP-65) when panel mounted |
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