Zmeter
Technical specification
Measurement specifications
| Parameter | Rating |
|---|---|
| Measurement Type | 4 electrodes |
| Maximum frequency | 200 000 Hz |
| Minimum frequency | 100 Hz |
| Minimum Number of point per measurement | 1 |
| Maximum Number of point per measurement | 255 |
| Frequency sweep within the specified range | Linear or logarithmic |
| Polarity Type | Normal or Inverted |
Electrical characteristics
| Parameter | Rating |
|---|---|
| Battery storage duration | 6 months (at 20–25 °C) |
| Battery type | Lithium-polymer rechargeable battery, 3.7 V nominal |
| Full charge duration | < 2h theoretical |
| Power input | 5VDC over USB-C |
| Operation during charge | Enabled – measurements can be performed while charging |
⚠️ Caution : Only use power adapters compliant with CE requirements and rated 5 VDC output . Use of non-compliant chargers may cause product damage or safety risks and will void the warranty.
Connectivity and control
| Parameter | Rating |
|---|---|
| Protocol | Bluetooth Low Energy (BLE) |
| Recommanded range | Up to 10 meters from the smartphone in line-of-sight (no obstacles) |
| Mobile application | Contextual Instruments, available on Android/iOS |
| Control features | Start/stop measurement, calibration, configuration, data visualization |
Case characteristics
| Parameter | Rating |
|---|---|
| Width | 51mm |
| Length | 58mm |
| Height | 16mm |
| IP code | IP20 |
| Material | Technical plastic (PLA) |
Environnemental and Usage Conditions
| Parameter | Rating |
|---|---|
| Operating temperature | +10 °C to +40 °C |
| Storage temperature | 0 °C to +45 °C |
| Relative humidity | < 85%, non-condensing |
| Operating environment | Indoor use only (laboratory, office, or medical setting) |
| Intended users | Professional users |
Maintenance and Precautions
- Do not immerse the product.
- Avoid exposure to heat sources, moisture, or direct sunlight.
- Do not attempt to open or repair the device; no user-serviceable parts inside.
- Discontinue use if the enclosure, cable, or battery shows visible damage (swelling, deformation, etc.).
Safety Information
- Stop using immediately if the product overheats or emits an unusual odor.
- Keep out of reach of children.
- Use only within the environmental limits specified.
Storage and Transportation
- Store in a dry environment, temperature between 0 °C and 40 °C.
- Avoid impact, vibration, or prolonged exposure to sunlight.
- If unused for more than 6 months, fully recharge the battery before long-term storage.
End-of-Life and Recycling
This product contains a rechargeable lithium-polymer battery and electronic components. In compliance with Directive 2006/66/EC and Directive 2012/19/EU (WEEE), this product must be collected separately and disposed of in an authorized recycling facility.
Let's measure !
- Before first use, connect the sensor to a USB-C power source (5 VDC) and allow it to fully charge.
- Power on the device by pressing the power button. The device will turn on and automatically enter BLE advertising mode.
- Open the Contextual Instrument mobile application and follow the on-screen instructions. All steps (from launching a measurement to visualizing data) are handled within the app. You will be prompted to specify a sensor setup, which defines the sensor configuration. More details are provided in the next section.
- To power off the device, press the power button once.
Wiring diagrams
Zmeter configuration (sensor setup)
This device is compatible with Contextual Instruments' mobile app. Please visit the Apple Store or Google Play to download it. In LIVE mode or when setting up a TRIAL, you can specify the acquisition parameters in the sensor setup. The Zmeter sensor setup comprises the following elements.
- Sensor setup name: The name of you setup. Name your setup wisely so you can easily reuse it when needed.
- Min frequency: Impedance measurements are taken at defined frequencies. A frequency sweep is performed between the specified minimum and maximum values. Set here the minimum value.
- Max frequency: Impedance measurements are taken at defined frequencies. A frequency sweep is performed between the specified minimum and maximum values. Set here the maximum value.
- Number of points: This corresponds to the number of frequency values at which measurements are taken within the Min/Max frequency range.
- Sweep Type: To distribute the selected number of points between the minimum and maximum frequency, the application allows two modes: linear (equal spacing between points) or logarithmic (equal ratio between points).
- Polarity Type: Impedance may vary depending on the direction of excitation. It is, however, possible to inject the signal through one electrode and measure with the other in normal mode, or reverse the roles in inverted mode.
- Delay before measurement: This parameter defines the delay (in seconds) before the Zmeter initiates measurement. The measurement process remains unaffected: regardless of the delay value, the Zmeter operates identically. If a delay >0 is specified, you will simply notice that the time between the start and the end of the measure is slightly longer (according to the delay specified).
Zmeter states
| State | LED Status | Definition |
|---|---|---|
| Sleep mode | off | The device is in sleep mode. It enters sleep mode after a press of its power button. |
| Charging | Plugged LED green | The device is connected to a power source |
| Charging | Charging LED orange | The device is charging. When fully charged, orange led will turn off. |
| Calibration | blinking green | Pressing the power button while the device is in sleep mode wakes it up and starts the calibration process. The process takes less than 20 seconds |
| IDLE | solid green | The device is ready to measure |
| Preparing mode | solid blue | The button has been pressed. The device is waiting for contact with a surface (e.g., skin) to start measuring |
| Measure mode | blinking blue | Measurement in progress! The buzzer will sound once at the start and twice upon completion. Do not move the Zmeter between these signals. |
| Error | blinking red quickly | The device has a problem with the data storage. |
| Error | blinking red slowly | The device has lost date and time |
| Any state | Any led status | Press the power button to swith it to sleep mode |
Resetting the device
Press the power button once, state LED will turn off. Wait 10s, then press the power button once again. Wait until state LED lights solid green.
CSV file
The CSV file of Zmeter measurements is structured in three parts: measurement metadata, bio-impedance measurement indicators, and the raw data.
Metadata
| Title | Definition |
|---|---|
| Sensor setup | Sensor setup name. |
| Sensor setup id | Sensor setup ID. |
| Sensor SN | Sensor Serial Number. This number is printed on the device. |
| Experimenter | Experimenter name. |
| Firmware version | Zmeter firmware version. |
| Date | Measurement timestamp. |
| Timezone | Timestamp timezone. The time zone associated with the recorded timestamp. |
| User note | User comments provided in the dedicated field. |
| Result data type(s) | Type of Acquired Data. |
| Device | Device type used. |
| Polarity | See Zmeter configuration section. |
| Sweep type | See Zmeter configuration section. |
| Measure type | See Zmeter configuration section. |
| Frequency start | See Zmeter configuration section. |
| Frequency stop | See Zmeter configuration section. |
| Samples number | See Zmeter configuration section. |
| Measurement check | Built-in Setting. Always set to true. Intended for debugging purposes only. |
| Premeasurement delay | See Zmeter configuration section. |
| Temperature | Measured by the Zmeter’s internal temperature sensor, which is located inside the device. Interpret the data with caution, as heat from the user’s hand may affect the measurement. |
| Humidity | Measured by the Zmeter’s internal humidity sensor, which is located inside the device. |
| Pressure | Measured by the Zmeter’s internal pressure sensor, which is located inside the device. |
Indicators
Three sets of indicators are available:
- Indicators based on raw data, labeled as
phase_modulus.
| Title | Definition |
|---|---|
| phase_modulus - P10_deg | Impedance phase at 10 kHz |
| phase_modulus - P200_deg | Impedance phase at 200 kHz |
| phase_modulus - P3_deg | Impedance phase at 3 kHz |
| phase_modulus - P50_deg | Impedance phase at 50 kHz |
| phase_modulus - Z10_ohms | Impedance magnitude at 10 kHz |
| phase_modulus - Z200_ohms | Impedance magnitude at 200 kHz |
| phase_modulus - Z3_ohms | Impedance magnitude at 3 kHz |
| phase_modulus - Z50_ohms | Impedance magnitude at 50 kHz |
- Two-time-constant model, labeled as
cpe_2_time_constants.
| Title | Definition |
|---|---|
| cpe_2_time_constants - Ceq1_F | High-frequency equivalent capacitance |
| cpe_2_time_constants - Ceq2_F | Low-frequency equivalent capacitance |
| cpe_2_time_constants - Qcpe1_F | High-frequency admittance of the constant phase element |
| cpe_2_time_constants - Qcpe2_F | Low-frequency admittance of the constant phase element |
| cpe_2_time_constants - R1_ohms | High-frequency parallel resistance |
| cpe_2_time_constants - R2_ohms | Low-frequency parallel resistance |
| cpe_2_time_constants - Rs_ohms | Series resistance |
| cpe_2_time_constants - a1 | High-frequency exponent of the constant phase element |
| cpe_2_time_constants - a2 | Low-frequency exponent of the constant phase element |
| cpe_2_time_constants - fc1_Hz | High-frequency characteristic frequency |
| cpe_2_time_constants - fc2_Hz | Low-frequency characteristic frequency |
| cpe_2_time_constants - r_squared | Coefficient of determination. It indicates how much of the observed data’s variance is captured by the fitted model. |
| cpe_2_time_constants - tau1_s | High frequence time constant |
| cpe_2_time_constants - tau2_s | Low frequence Time constant |
- Single-time-constant model, labeled as
cpe_1_time_constant.
| Title | Definition |
|---|---|
| cpe_1_time_constant - Ceq1c_F | Equivalent capacitance |
| cpe_1_time_constant - Qcpe1c_F | Admittance of the constant phase element |
| cpe_1_time_constant - Rp1c_ohms | Parallel resistance |
| cpe_1_time_constant - Rs1c_ohms | Series resistance |
| cpe_1_time_constant - a1c | Exponent of the constant phase element |
| cpe_1_time_constant - fc1c_Hz | Characteristic frequency |
| cpe_1_time_constant - r_squared | Coefficient of determination. It indicates how much of the observed data’s variance is captured by the fitted model. |
| cpe_1_time_constant - tau1c_s | Time constant |
Raw data
The raw dataset includes three columns: Frequency (Hz), Zr (Ω), and Zi (Ω), where ‘r’ stands for the real part and ‘i’ stands for the imaginary part.