In the development of automotive electrical control systems, it is important to measure and validate a diverse array of current levels among components such as:

• Drive current of various motors in the order of several amperes
• Inrush current, for example at motor start, in the order of several tens of amperes
• Minute control signals of about 1 mA
• Standby current

The need to measure such a wide range, from micro standby currents to inrush currents that can reach tens of amperes traditionally necessitate the use of separate sensors equipped with the appropriate range so that resolution and accuracy are not sacrificed. Using a higher range current sensor to measure low standby current will reveal no meaningful result, while sensors with a low range will not be able to handle high currents safely.

Hioki provides a solution for this particular application with the CT6710 (50MHz bandwidth) and CT6711 (120MHz bandwidth)  current probes (based on the zero-flux current sensing method using Hall Element detection), both of which offer three separate ranges to meet an expansive range of measurements in a single unit. More on this below:

Zero Flux AC/DC Current Sensing using Hall Element

In the zero-flux method, in order to cancel out the magnetic flux produced inside the magnetic core by the AC current flowing in the conductor being measured, a secondary current flows to the secondary side of the feedback winding. The magnetic flux existing in the low-frequency regions that cannot be cancelled is detected using a CT, Hall element, or Flux gate element, upon which a secondary feedback current is generated through an amplifier circuit so as to cancel out the magnetic flux in the low Hz regions. This secondary current flows to the shunt resistor, producing a voltage that is proportional to the current flowing in the conductor being measured.

The Hall element detection method is represented by the Hioki Models 3273-50 , 3274 , 3275 , 3276 , CT6700 , CT6701 , CT6710 , and CT6711 , all of which deliver the following key characteristics:

• Similar to the CT detection method, sensor operation depends on canceling out the magnetic flux in the magnetic core, giving it excellent linearity unaffected by the magnetic core’s B-H magnetic characteristics.
• Since the probes operate using the CT of the secondary feedback winding in the high-frequency region, and utilize an amplifier for the low-frequency region, a broad frequency bandwidth is supported.
• Like the flux-gate element detection method that will be discussed in the next installment, due to lack of excitation current noise, overall noise is extremely low.

Note that:

• The Hall element used in Hioki current probes is developed and manufactured in-house using a compound semiconductor called indium antimonide (InSb), which while delivering high-sensitivity, is susceptible to temperature drift due to its sensitivity to the surrounding temperature.

Because the zero-flux method achieves extremely stable measurements by driving the negative feedback characteristics of the magnetic circuit, thus reducing the effects of the magnetic core, it is capable of delivering a wide frequency band and improved linearity, factors that contribute to the optimization of the current sensor’s performance. Such characteristics are ideal for these AC/DC applications:

• Current testing of ECU and instrumentation systems in automobiles, e.g., dark current, large current, operating current of various motors
• Current consumption testing of wearable devices, e.g., battery-operated devices and their sensors
• Performance evaluation of high speed switching devices, e.g., monitoring the current waveform of SiC, GaN or other types of advanced components

330-Channel Portable Logger Delivers 1 Ms Sampling, Even Over Wireless Connections, Available with Your Choice of Plug-In and Wireless Units

Hioki is pleased to announce the launch of the Memory HiLogger LR8450 and LR8450-01.

■ DEVELOPMENT BACKGROUND　
Customers in the automotive and environment/alternative energy sectors, both of which Hioki has identified as priority markets, have embraced the legacy Memory HiLogger LR8400 series (max. 10 ms sampling), which can measure a large number of channels despite its compact size, and the popular Wireless Logging Station LR8410 (max. 100 ms sampling), which separates data measurement (by units) and collection (by the instrument).

Common themes appearing in feedback from LR8400 and LR8410 users included a desire to measure large numbers of channels more quickly in development of products such as electric vehicles (EVs), to measure strain on vehicle chassis and batteries along with temperature, and to reduce wiring man-hours and measurement issues by capturing strain data wirelessly.

■ KEY FEATURES
1. Sample a Large Number of Wired and Wireless Channels at Up to 1 ms
Customers need measurement solutions that are capable of accommodating abrupt changes in load in the development of electric vehicles such as EVs, hybrids (HVs), and plug-in hybrids (PHVs).  By using the High Speed Voltage Unit U8553, a 5-channel plug-in unit that can measure voltage at a sampling rate of 1 ms, customers can capture such rapid changes.

The LR8450 series is ideal for capturing output data from sensors that measure low-frequency (from 10 to several dozens of hertz) data such as resin pressure or vibration, which are difficult to measure at conventional sampling speeds. The Wireless High Speed Voltage Unit LR8533, a 5-channel wireless unit, can measure voltage at a sampling rate of 1 ms. This sampling rate is 100 times faster than the LR8410 Wireless Logging Station.

2. A Single Solution for Dynamic Strain Measurement

The Strain Unit U8554 (a plug-in unit) and the Wireless Strain Unit LR8534 (a wireless unit) are also capable of sampling data at up to 1 ms, making them useful in testing strain on vehicle chassis and brakes.

3. Add Wired or Wireless Channels as You Need Them

The LR8450-01 can also connect to seven wireless units. Combined with its four slots for plug-in units, that means you can pair up to 11 units, allowing one LR8450-01 to measure as many as 330 channels.   You can choose whether to use wireless connectivity for measurements as conditions dictate.

■ PRINCIPAL APPLICATIONS
• Testing of automobiles, farm and construction machinery, and electric devices
• Embedding in preventive maintenance systems for production equipment and evaluation equipment at manufacturing plants

■ SERIES LINEUP
Memory HiLogger  LR8450 (standard model)
Memory HiLogger  LR8450-01 (wireless LAN model)
Voltage/Temp Unit U8550 (15 channels, plug-in)
Wireless Voltage/Temp Unit LR8530 (15 channels, wireless)
*Example units shown (a total of five plug-in and five wireless units are available).
*Hioki plans to launch all wireless units in 2020.

^*1 Strain: The ratio of the change in the form of elongation and contraction that occurs in an object when a force is applied. The minuscule change in electrical resistance caused by strain is detected and measured using a strain gauge.
^*2 If four Voltage/Temp Unit U8552 (30 channels, plug-in) units and seven Wireless Voltage/Temp Unit LR8532 (30 channels, wireless) units are connected, the LR8450-01 can measure 330 channels of voltage and temperature data at a maximum sampling rate of 20 ms.
^*3 Strain gauge: A sensor for measuring strain.

Introducing a Pair of AC Ammeters Engineered to Accommodate Large-Diameter Cables with All the Ease of Use You’ve Come to Expect from Hioki

Hioki is pleased to announce the December 2019 launch of the AC Clamp Meter CM3281 and CM3291, a pair of large-diameter AC ammeters featuring a more compact jaw (sensor) design that makes them easier to insert between wires in confined spaces.

■ ENHANCEMENT OF THE POPULAR LOW-PROFILE DESIGN
The previous AC Clamp Meter CM3289 (⌀33 mm, rating of 1000 A AC) featured a low-profile design that was engineered to enable users to clamp around wires easier. The new instruments build on that product’s design by increasing both the jaw diameter (⌀46 mm) and the current capacity (by increasing the rating to 2000 A AC). Both new models preserve the CM3289’s ease of use so that thick cables (paired wires, etc.)¹ are easily measured.

Hioki has redesigned the jaw (sensor) profile as part of an effort to expand its clamp meter line with models that are easier than ever to clamp around wires. The newly designed clamp meters have won broad praise, including an honorable mention in the 58th Product Competition at Electrical Construction Equipment and Materials (JECA) Fair 2019² and a 2019 Good Design Award³.

Although Hioki has recently updated many of its clamp meters, up until now only one low-profile model has been capable of measuring thick cables (paired wires, etc.). To address this issue, Hioki developed the CM3281 (mean value rectification method) and CM3291 (true RMS method) to enlarge the 33 mm diameter and 1000 A AC current rating of the AC Clamp Meter CM3289 to 46 mm and 2000 A AC, respectively.

■ KEY FEATURES
1. Designed to accommodate larger-diameter wires without compromising ease of use
The CM3281 and CM3291 are as easy to clamp around wires as their predecessor, the CM3289. Since their jaws are only 8.3 mm thick, they can be easily clamped around wires in confined spaces. And since they can accommodate conductors with a diameter of up to 46 mm, they can measure thick wires (for example, paired wires) that would require use of an option with the previous CM3289.

2. Built tough for use in the field
Thanks to a broad operating temperature range of -25°C to 65C°, the CM3281 and CM3291 can be used almost anywhere. What’s more, drop-proof construction means the instruments can withstand being dropped onto concrete from a height of 1 m.

 3. Ability to measure up to 2000 A AC using either the mean rectification method or the true RMS method
The CM3281 uses the mean rectification method to generate indicated values that approach the fundamental wave component.  On the other hand, the CM3291 uses the true RMS method, which yields accurate values even when the AC current waveform is distorted, for example due to use of an inverter or switching power supply.  Customers can choose the model (measurement method) that best suits their application.

4. Ability to measure both current and voltage
The CM3281 and CM3291 can measure a variety of parameters besides AC current in a single unit, including AC/DC voltage, continuity, and resistance.

■ PRINCIPAL APPLICATION
Equipment maintenance inspections

¹ Paired wires: Cables that have been split into two wires in order to carry a large current.

² Electrical Construction Equipment and Materials (JECA) Fair: Japan’s largest electrical equipment exhibition. The event is organized by the Japan Electrical Construction Association with sponsors including the Ministry of Land, Infrastructure, Transport and Tourism; the Ministry of Economy, Trade and Industry; and the Ministry of the Environment. The AC/DC Clamp Meter CM4376 received a JECA honorable mention in a previous exhibition’s Product Competition. Hioki products have received a total of 9 awards since the 44th fair in 1996.

³ Good Design Awards: A comprehensive design assessment and recommendation program organized by the Japan Institute of Design Promotion with more than 50 years of history. The AC/DC Clamp Meter CM4375/CM4376 and AC Clamp Meter CM4141/CM4142 received 2019 Good Design Awards.