Display Unit CM7290

DISPLAY UNIT
CM7290

Multi-functional Display Unit to Use Right on the Field or
Output to Advanced Recorder or Logger
Exclusive Academic Offer

Hioki clamp on meters are best-in-class measuring devices incorporating Hioki’s expertise in current sensing technology. The CM7290 is the display and output unit for the CT7600 and CT7700 AC/DC Current Sensor series, creating a standalone clamp meter for field use or enabling waveform signals to be output to a Hioki memory recorder or logger for further analysis.

Key Features
• Power supply and signal output for Current Sensor CT7000 series
• Simultaneous dual display of the measured values, frequency, and output rate
• Four output formats to output data to loggers or other devices (via Display Unit)
• Supports AC adapter, AA alkaline batteries, and external power supply

Model No. (Order Code)

CM7290 For the CT7000 series
Note: CM7290, CM7291 cannot be used alone. Use with CT7000 series. When used in combination with the CT7000 sensor series, the frequency band for current display and waveform output is narrower than the sensor band.
Current Measurement Using an AC/DC Current Sensor: Basic Measurement Settings

By connecting an AC/DC current sensor to the Display Unit CM7290 and the Display Unit to a data logger or Memory HiCorder, you can output:
• A DC or AC (up to 5 kHz/10 kHz) current waveform as-is (using WAVE mode for waveform output)
• An analog signal generated by converting the input waveform to a series of RMS values (using RMS mode for RMS output)
• An analog signal generated by detecting the current waveform’s peak value (using PEAK mode for peak output
• An analog waveform generated by detecting the frequency of the current waveform (using FREQ mode for frequency output)

Current Measurement Using an AC/DC Current Sensor: Compatible Current Sensors

You can use any of a selection of available AC/DC current sensors with ratings ranging from 100 A to 2000 A. The CM7290 supports two types of current sensor: AC/DC Auto-zero Current Sensors, which have a sensor frequency band ranging from DC to 5 kHz AC, and AC/DC Current Sensors, which have a frequency band ranging from DC to 10 kHz AC.

Current Measurement Using an AC/DC Current Sensor: Auto-Zero Current Sensor Functionality

Because temperature variations cause the zero-point to shift when using a conventional DC current sensor to measure DC current, it is necessary to perform zero-adjustment periodically when recording data over an extended period of time with such a sensor. This shortcoming is caused by the effects of the Hall element that conventional DC current sensors use to to detect current. Hioki’s new auto-zero current sensors incorporate a new switching-based offset cancellation circuit developed to address this problem. The new design minimizes zero-point shift, making it possible to record DC current values over an extended period of time without the need for periodic zero-adjustment.

Current Measurement Using an AC/DC Current Sensor: WAVE Waveform Output Function

The Display Unit CM7290 converts the current waveform for current flowing in a wire to which an AC/DC current sensor has been applied to a proportional voltage signal. By inputting that signal to a digital oscilloscope or Memory HiCorder, you can measure instantaneous AC or DC current waveforms such as a motor’s starting current waveform. Alternatively, by using the CM7290’s WAVE waveform output function in combination with a data logger, you can observe the DC current generated by a PV system’s solar panels over extended periods of time. Auto-zero current sensors are ideally suited to applications in which a DC current must be observed over an extended period of time.

Current Measurement Using an AC/DC Current Sensor: RMS Mode for RMS Output

In this mode, the Display Unit CM7290 converts the current waveform for current flowing in a wire to which an AC/DC current sensor has been applied to a series of RMS values. It then outputs the result as a voltage signal (FAST: 45 Hz or greater, NORMAL: 10 Hz or greater, SLOW: 3 Hz or greater). This configuration is ideally suited to applications such as AC current measurement on the power supply side of a welding machine, which is characterized by abrupt current fluctuations, or long-term measurement of RMS values for the current waveform from an inverter operating at varying frequencies or a machine tool’s spindle motor.

Current Measurement Using an AC/DC Current Sensor: PEAK Mode for Peak Output

In this mode, the Display Unit CM7290 detects the peak value of the current waveform for current flowing in a wire to which an AC/DC current sensor has been applied at the rate of 2 kS/s (= 500 μs). It then outputs its absolute value as a voltage signal with an output refresh time of 0.02 s (FAST), 0.2 s (NORMAL), or 1 s (SLOW). This configuration is ideally suited to applications in which the maximum current value of a rapidly fluctuating power supply line or load must be continuously recorded.

Current Measurement Using an AC/DC Current Sensor: FREQ Mode for Frequency Output

In this mode, the Display Unit CM7290 calculates the frequency of the current waveform for current flowing in a wire to which an AC/DC current sensor has been applied at the user-specified interval. It then outputs the result as a voltage signal with an output refresh time of 0.2 s (FAST), 0.2 s (NORMAL), or 3 s (SLOW). In this configuration, the CM7290 can be used in applications such as frequency fluctuation inspections and testing of compressors and motors.