General, application fields
Precision power measuring – this associates to the ZES ZIMMER power multimeter series,
• LMG90 and LMG95 for monophase
• LMG310 and LMG450 for multiphase measurements.
Both series are successful, approved and kept state of the art by continuous and steady research and development by the ZES ZIMMER engineering staff. Due to its high sampling rate, simultaneous for all channels, the LMG310 is capable of performing extremely accurate measurements of power and energy in symmetrical and non-symmetrical 3-phase systems with any load and signals with frequencies from DC to 1MHz. The wideband fully floating isolated inputs have a high immunity against electrical disturbances and a very high dynamic common-mode rejection, and feature wide measuring ranges: for current directly from 3mA to 30A, for voltage directly from 1V to 1000V. Measuring inputs for external
shunt voltages extend the measuring ranges for the current in any way. This design of the wideband measuring inputs and the processing in real time with digital signal processors give reason for the preferred use of the LMG310 in measuring applications of pulsed power electronics (also at PWM-converters). The LMG310 is used in the fields of development, manufacturing and quality control. There the simultaneous threephase measurement of active power loss in reactive and nonlinear components like transformers, chokes, motors, capacitors is required; the power consumption and efficiency of power supplies, electrical lamp ballasts and inverters have to be specified. Analysis of harmonics including the limit check of the harmonics according IEC61000-3-2 (classes A, B, C and D), the flicker measuring according IEC61000-3-3 and transient recording and monitoring are available options of the LMG310. These three options
are used to evaluate the power line disturbances which may be emitted by electrical devices, further to analyse the quality of supplied power in the mains. The option to measure the loss power or transformers (transformer version) serves to measure the losses at very low cosj (<0.01) with an error <0.006% related to the power range. By means of the integrated formula editor all measured and calculated quantities as well as the signals of the processing signal interface (option) can be computed to new quantities and displayed on the screen. The time diagrams of the signals of the screen in real time (option scope-/plot function) is another powerful feature of the instrument. Driver for modern instrumentation and evaluation software like LabVIEW® are available as well as user programmes built and compiled by means of these software tools. When connecting the LMG310 with a PC you easily can build measuring systems, motor and other test systems.
Easy to use
The high-resolution screen with the status line for input levels, cycle time and synchronization, the 10 softkeys on the bottom and right margin of the screen and the 15 menu keys for access to important menus provide a clear, simple
and intuitively comprehensible operation of the instrument. To indicate the desired information, it is normally sufficient to press just one key. Menus for the instrument setup (configurations) as well as menus defined by the user for measuring values display can be stored and recalled when needed.
Interference immunity, dynamic common-mode rejection
The LMG310 has a high interference immunity, which is defined according IEC61000 (e.g. bursts up to 4kV on all measuring and supply-inputs) and widely exceeds the standards. In addition the excellent common- mode rejection of the instrument ensures the correct sampling and computing of measuring values even for measuring arrangements floating against earth with high frequencies (>100kHz), voltages up to 1000V and high slew rates (>20kV/μs).
Measuring circuits
The LMG310 is suitable for all measurements of 1-, 2- and 3- phase systems. The measuring channels can be used independently. When using the option star/delta conversion the input signals applied as phase and/or linked values will be evaluated according their wiring (current/ voltage as ; ; ; ) and will be transformed. In the figure the use of the softkey ´LINKED VALUES´ has activated a menu with the phase values (index 1p, 2p, 3p) and the linked values (index 12, 23, 31) for current, voltage and power. The magnitude physically applied to the measuring channel and directly measured is indexed with one digit only (index 1, 2, 3), as you see in the measuring value display on the front page. The measurement with Aron measuring circuit (3-phase with 2 measuring channels) is also supported, so that the third measuring channel is available for additional measurements.
Measuring inputs, measuring accuracy
The measuring error (as sum of the percentages of reading and measuring range) for current and voltage is <1% valid for the whole precision range from DC to 400kHz. The basic accuracy is 0.05%. This accuracy is valid for all current and voltage measuring ranges (3mA-30A, 1V-1000V)! Above the 400kHz precision range measurements with high accuracy are also possible because of 1MHz bandwidth of the input channels. The measuring accuracy will be decreased by the derating, starting at 400kHz. Commonmode signals in the precision range up to 400kHz have nearly no influence to the measuring results. The measuring inputs for external shunt voltages with the ranges 15, 50, 150mV enlarge the measurements for currents. In all current and voltage measuring ranges the LMG310 is capable of measuring up to the double nominal value, max. 60Apeak and 2000Vpeak.
