Single Channel Capacitance Wireless Probe System
A Bluetooth 2.4GHz wireless capacitive-gap sensor to accurately measure the distance to a grounded metal target
The system is a 2.4GHz wireless capacitive gap sensor paired with a receiving device. Both the transmitter “sensor” and receiver devices are “Bluetooth” radio frequency transceivers. They both are capable of transmitting and receiving digital packet messages. Multiple sensor and receiver devices may be operated in a close environment as they will not interfere with each other. Users can program and calibrate the Probe assemblies with MTI provided software.
| Bluetooth Wireless | Proven to work in noisy industrial environments and is immune to jamming by other wireless devices. |
| Capacitance-based Technology | Unlike eddy current, capacitance is insensitive to target material, self-contained absolute calibration |
| Standard PLC Interface | Easy to hook up to a PLC without any custom wiring |
| Networking Capable | Up to 4 sensors can be networked together per receiver, for rich geometrical measurement |
| Battery-operated Compact Form Factor | Can be easily placed in hazardous or unserviceable environments like in rotating machinery |
Probe / Transmitter Specifications
| Measurement Range | 0.1-2.0 mm |
| Resolution | 0.014 mm |
| Accuracy | 0.043 mm |
| Linearity error | 0.3% FSR |
| Max sample rate | 4 SPS |
| Max latency | 2 seconds |
| Power | 3.4 – 4.5 VDC (1x 3.6V LTC battery) At 5 mA |
| Radio frequency | 2.4GHz |
| Maximum distance from receiver device | 5 m (Mounting dependent) |
| Maximum number of devices in close proximity | 30 units |
| Radio Frequency Conformity | IEEE 802.15.1 (ISM standard) |
| Size | 10 mm dia x 60 mm long |
| Weight | 10.5 grams |
| Antenna connector required | Hirose U.FL-LP-040 |
| Battery connector | SURS # SM05B-SURS-TF |
| Mounting thread | 10 mm x .75 |
| Battery life | Dependent on SPS and Sample Period |
Sensor System Receiver Specifications
The following specifications are listed for the “Standard” configuration.
Contact the factory for specifications of other versions.
| Measurement Range | 0.1-2.0 mm |
| Power | 5-30 VDC, 100mA |
| Interface Protocol | RS-485 Modbus RTU |
| Protocol Baud | 19200 |
| Protocol Parity | Even |
| Protocol Stop Bits | 1 |
| Device Address | 0x42 (may be adjusted) |
| Operating Temperature | 4 to 55ºC |
| Storage Temperature | -15 to 65ºC (5 to 150ºF) |
| Radio frequency | 2.4 GHz |
| Maximum distance from sensor | 5 m (Mounting dependent) |
| Radio Frequency Conformity | IEEE 802.15.1 (ISM standard) |
| Size | 15 mm H x 44 mm W x 64 mm L |
| Weight | 4 oz |
| Connector | Phoenix Contact #1844263 |
| Mate | Phoenix Contact #1840382 |
Replacement of out-dated Eddy Current probe systems
- Eliminate drift due to temperature, by replacing eddy current probes with higher temperature stability capacitance.
- Gain more insight by networking wireless probes together to measure target geometry
- Built-in calibration replaces in-situ Eddy Current calibration saving installation time
- Immune to magnetic field interference
Measuring gap in rotating machinery
- The wireless capability and compact form factor, were designed specifically to measure gap in difficult to reach or inaccessible locations
- Optimized for machines that have a surface velocity up to 6000 SFM
- Capacitance-based technology allows measurement to any type of metal surface
The system is a 2.4GHz wireless capacitive gap sensor paired with a receiving device. Calibrated, it measures the distance to a grounded metal target. The transmitter can be permanently mounted on a fixture or threaded probe holder using two jam nuts. The probe/transmitter unit has two connectors. One connector is to attach the antenna and the second connector is to attach the battery for portable operation. Typically, the battery Amp hours is sized for the application. The receiver communicates with up to 4 wireless displacement sensors to receive displacement readings. The receiver interfaces as a RS-485 Modbus RTU device. The receiver device must also be connected to a suitable power supply. A “start sample” command is sent to the selected sensor to begin receiving data at a selected rate.
For single samples, a manual sample sequence command can be executed at any point. The sample sequence puts the sensor into a powered on state for a single sample cycle. Upon completion of the cycle, the sensor transmits the data and goes back to a low-power state. Both the transmitter “sensor” and receiver devices are “Bluetooth” radio frequency transceivers. They both are capable of transmitting and receiving digital packet messages. Multiple sensor and receiver devices may be operated in a close environment as they will not interfere with each other. Users can program and calibrate the Probe assemblies with MTI provided software.
MTI capacitance measurement system is based on the principle of parallel plate capacitor measurement. The electrical capacitance formed between a capacitance probe and a target surface varies as a function of the distance (gap) between these two surfaces. Capacitance-based measurement probes have long been employed as a means of non-contact measurement of electrically conductive materials. In a typical system, MTII’s capacitance probe acts as one of the plates and the grounded target the other plate. MTI’s amplifier converts the gap’s capacitance into an output voltage proportional to the gap. Capacitive measurements are very stable rivaling interferometer accuracy. The Capacitance is not adversely affected by temperature, humidity and pressure.
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