Description

ACL series loads are suitable for DC and AC voltages up to 1,000 Hz. There are single-phase models as well as three-phase loads which combine 3 channels or phases, respectively, in one housing. Ethernet, USB, RS-232, CAN, I/O interface and a system bus for Master-Slave operation are built in as standard, a GPIB interface is available as an option. Programming is done in SCPI.

Operating Modes

The ACL series loads have constant current, constant resistance, constant power and constant voltage modes (CC, CR, CP, CV Mode). In AC operation, the set waveform is applied to the load current, independent of the input voltage. In resistance mode, the current level and waveform depend on the level and waveform of the input voltage. In power and voltage mode, the power or voltage is controlled by software by adjusting the input current.

Input Mode, Synchronization

The input mode defines the kind of voltage the electronic load expects at the input:

• DC: direct voltage
• AC: alternating voltage within the specified frequency range with synchronization to input voltage, line/mains voltage, external signal

Protection, Monitoring

• Adjustable overcurrent protection
• Overpower protection
• Overtemperature protection
• Overvoltage indication
• Undervoltage indication

I/O Port (Option ACL06)

All inputs and outputs of the optional I/O port are galvanically isolated from the load input. The control inputs can be operated by 2 ... 24 V. Signals for:

• Analog load setting from 0 ... 5 V or 0 ... 10 V in CC mode
• Operating mode selection
• Input mode (AC, DC)
• Synchronization source (input, line, extern)
• Load activation
• Control source selection (intern, extern)
• Trigger input
• Trigger output
• Synchronization input
• Remote shut-down input
• Analog voltage monitor output 0 ... 10 V
• Analog current monitor output 0 ... 10V
• Analog monitor outputs as proportional AC curve or rms value, selectable
• Programmable digital output
• Status output for load input activation
• Status output for overload

Single and 3-Phase Loads

Besides single-channel AC loads ACLS, the models of the ACLT series have been developed for loading three-phase systems. They combine 3 AC load channels in one housing. The 3 load channels can be used to load 3 different DUTs in AC or DC operation or to test a three-phase system. In the so-called balanced mode, all channels are loaded with the same setpoint and the same waveform. In synchronization mode Line, channel A synchronizes to the mains voltage, channels B and C are each phase-shifted by 120°. To increase the maximum load current, several channels of an ACLT three-phase device or several ACLS single-phase devices can be connected in parallel. Several single-phase devices can be connected to form a Master-Slave system.

User Interface

In addition to the load input, which is controlled by a large push-button, and the rotary knob for adjusting the setting value, the devices are operated by intuitive menu navigation via a 4.3" touch display like it is known with smartphones. The most common functions can be accessed via shortcuts. An associated help window is available for each dialog window, explaining the meaning of the respective elements. The help language can be set to German or English.

Mouse

If you prefer to operate by mouse, you can use the USB port on the front.

Manual on Board

The ACL series user manual is stored in PDF format in the internal device memory. This can be copied to a USB flash drive or, conversely, updated from a USB flash drive if a newer version is available, e.g. after a firmware update with new functions. Thus, the user manual corresponding to the installed firmware doesn't get lost.

Waveforms

• Crest Factor, Phase Cut, Phase shift

For sine waveforms the crest factor (CF) can be adjusted from 1.4142 to 4.0. The load corrects the resulting amplitude so that the RMS value remains constant. For each waveform, a phase cut (PC) and a phase shift (PS) of the current waveform can be set in the range from -180 to +180°. Depending on the phase angle, the RMS value of the current changes. The phase shift must be combined with a phase cut or a crest factor. A phase shift in the sense of a purely capacitive or inductive load is not possible.

• Harmonics

In the waveform with harmonics, the amplitudes of the basic wave normalized from 0 to 1 as well as the up to 24 harmonics (even and odd) are summed up. The load corrects the resulting amplitude so that the RMS value remains constant.

• Arbitrary Waveforms

The definition of a period with 360 single points ensures maximum flexibility. The basis is either a sine, a square or a triangle signal, which can then be changed point by point. Depending on the waveform, the RMS value of the current changes.

Load Profile (LIST Function)

In all operating modes, the ACL load can emulate load profiles by means of the LIST function. Up to 300 setpoints of variable duration with associated ramp times are possible. In AC mode, the LIST function serves as a load profile of RMS values with the active waveform. Sampling times can be defined separately for each list section. Voltage and current are measured synchronously and stored with a time stamp.

Rectangular Function

Likewise for all operating modes, the rectangular function offers a simple variant for changing between 2 setting values with adjustable durations. In AC mode, the rectangle function serves as a load profile of 2 rms values with the active waveform.

DAQ Acquisition (DAQ)

The electronic load can also store synchronous data records of voltage and current with time stamp in a defined interval, independent of the LIST function. Up to 40,000 data records are stored in a ring buffer. Once recording is complete, the data is read out via a data interface or transferred to a USB flash drive.

Static Data Logging

During slow processes, the electronic load can store voltage and current with timestamps directly on a USB flash drive in local mode. Sampling intervals are in the range of seconds.

Trigger Model

In remote operation via a data interface, several functions can be activated by a configurable trigger event:

• Activation/deactivation of list execution
• Activation/deactivation of data acquisition
• Activation/deactivation of load input
• Setting of all triggered setting values of all operating modes

Available trigger sources: Extern, Bus.

Save Settings

In order to quickly reconstruct frequently recurring test tasks, the settings active in the electronic load can be stored non-volatile so that they can be reloaded later on. 9 memory positions are available. The ACL load can optionally set the reset state when switching on, the last active settings at power-off or memory positions 1 to 9.

Watchdog Function

To protect the DUT from communication problems, the electronic load in digital remote control mode has a watchdog function that switches off the load input if the previously programmed watchdog delay time expires without the watchdog being reset. The watchdog delay time is set by SCPI command, another command activates the watchdog. When the watchdog is active, a control program must ensure that the command to reset the watchdog is periodically sent to the electronic load.

Display of Measurements

Depending on the focus on the display, more or less measured values are shown per channel. A single-phase ACLS device displays the following measured values in the main display: RMS value voltage, RMS value current, resistance, active power, apparent power, reactive power, frequency, power factor, crest factor. If all channels ABC of a multi-channel or three-phase device are focused, the effective value of the voltage and the effective value of the current are displayed for each channel. All these measured variables can be queried via one of the data interfaces using a SCPI command.

Waveform Display

The last measured period of current and voltage is measured with 360 points and displayed in the Measured Waveform dialog.

Yt Graph

The Yt-Graph shows the time course of the RMS value of voltage, current and/or power of the focused channel.

Calibration 

A free Factory Calibration Certificate (FCC) is supplied with the devices. The calibration process is subject to supervision in accordance with DIN EN ISO 9001. The calibration certificate documents the traceability to national standards to illustrate the physical device in accordance with the international System of Units (SI). Within the 2-year warranty period, we will calibrate a second time free of charge if the respective device (serial number) will have been registrated at H&H.

--> Conditions for a second free calibration

For use under laboratory conditions, H&H recommends a calibration interval of 2 years. This is an empirical value that can be used as a guide for the first period of use. Depending on the intended use, service life, relevance of the application and ambient conditions, the operator should adjust this interval accordingly.

Documentation

We supply a user manual as pdf file (also saved in the electronic load) and printed General Safety Instructions, each in German and English.