Terms and definitions

Terms and definitions for the specification of FuG power supplies

Ambient temperature

All data in our catalogue are valid for an ambient temperature range of 0 – 40°C. This is the standard temperature range. Other environment temperature on request.

Absolute accuracy

The stated figure refers to the absolute deviation of the DVM, or of the monitors of the analogue programming. They are independent of the stability data of the individual series.

For all families with standard data the following absolute accuracy values apply:

for all nominal currents:

< ± 0,2% of the nominal value

for all nominal voltages:

for all nominal currents:

within the range > 5 mA up to < 200 A:

< ± 0,5% of the nominal value

for all nominal currents:

< ± 0,2% of the nominal value

< ± 0,2% of the nominal value

without this range:

< ± 2 Digits

Active pull-down control

Available on demand especially for the NLN series: Power transistors parallel to the output acting as a current sink. In customer-specific power supplies also otherwise possible.

Analogue programming

The standard analogue programming allows an adjustment of voltage and current by an external DC voltage of 0 – 10 V, as well as the read-out of the actual values on monitor terminals (normalized to 0 – 10 V) – see also Description of analogue programming.

Analogue programming, floating

Function as analogue prorgramming, but isolated from the FuG power supply up to 2 kV DC – see also Description of floating analogue programming

Autoranging power supply

FuG Power supply with automatically ranging of the operating point without steps. Within a fixed power limitation the the operating characteristic of the power supply is extended to both the sides of higher voltage and higher current.

Bipolar power supply

A bipolar power supply can be adjusted from positive output voltage and current to negative with continuous zero crossing. All bipolar power supply units of FuG Elektronik GmbH are designed for restricted 4-quadrant operation. The electrical power, produced by the power supply, can be consumed again with some time-shift. On request the units can be equipped with full 4-quadrant capability.

Current control

Standard power supplies can be operated in constant voltage or constant current mode. The switchover occurs automatically with a sharp transition.

CE mark

All FuG power supplies have a CE label – a guarantee of compliance with the current EMC and safety standards.

Certificate of calibration

All FuG power supplies can be calibrated at the factory. The certificate of calibration, which can be given to the customer on request, confirms the compliance of the output data with the catalogue data e.g.:

  • Indication on the DVM
  • Monitor voltages*)
  • Computer output data*)
  • Reference voltage*)
  • Linear coherence between control voltage and output value*)

*) Options

Current limitation

When a FuG power supply operates with constant voltage, the current potentiometer can be used for setting the current limit value.

Charging power

Power specification for FuG capacitor charging power supplies. The data is in J/s, and is valid for charging from “0” to the nominal voltage. For charging of a partially discharged capacitor a considerably higher charging power, up to the doubles, can be supplied.

Charging current

FuG capacitor charging power supplies operate with constant current. It is adjustable to every value up to the nominal value. On request units available with enhanced charging current at low voltage.

Chopper controlled

see Switch mode power supply.

Discharge time constant

This data always relates to the unconnected output. It is the time which the output voltage has to decay to approx. 37% of the adjusted voltage after the output has been switched off.


Since 1994 FuG Elektronik GmbH has maintained this quality assurance system. All supplied units are tested (using calibrated measuring instruments) and the results recorded in our test department, so as to ensure that all units shipped are fully in accordance with their specification.

Deviation (Stability data)

This term assumes the following data which are always refer to the nominal value and are valid for constant operating conditions. Constant conditions means that, in each case, all other conditions such as the load, ambient temperature and mains voltage are constant:
a) Deviation of the output voltage (or output current when specified) for ±10% variation of the line voltage.
b) Deviation of the output voltage (or output current when specified) over a period of 8 hours, after an appropriate warm up time.
c) Deviation of the output voltage at load changes from full load to no load.

Double stabilized power supply

Such units are equipped with a linear transistor regulator and a thyristor pre-stabilization. So the high efficiency of the thyristor controller is combined with the good regulation characteristics of a linear regulator.


Fast discharge switch for controlled discharging of internal and external capacitors. This kind of switch has to be specified always according to the application and is not a standard component. A dumpswitch is often used in combination with an interlock. (see also Interlock)

Electronic load

Unit, which has the behavior of a adjustable load resistor. Usually it is used for testing FuG power supplies. Depending on the design, there can be adjusted and stabilized the resistance, the consummated power the or consummated current.


Electro Magnetic Compatibility – for standards see CE mark.
EN61000-6-1 and EN61000-6-3 (single-phase mains connection)
EN61000-6-2 and EN61000-6-4 (two- and three-phase mains connection)
Safety: EN61010-1


19″ cassette system cases, 3 HU


We state no defined values for efficiency since it depends upon the operating point of the power supply. For typical efficiencies check here.

Fast de-energizing

Option for super conductor supplies for controlled de-energizing of super conducting coils/magnets at quench.

Final charging voltage

Preset voltage for capacitor charging power supplies up to which the capacitor shall be charged.


Height unit in 19″ system. 1 HE=44.5 mm.


Older size of plug-in cases, 4 HU


Loop for safety switching off when disconnected. Mains disconnection but without forced discharging of the output or load. If a forced discharge is mandatory for having greater safety, we recommend combination with a dump switch. Additional measures are still required for personal safety. (see also dump switch)

longitudinal regulator

see linear regulator

Light flux regulation

Lamp ballast units can have optionally a terminal for the connection of a photo-sensor to control the intensity of the lamp.

Linear regulation

Control of energy flow by one or more of bipolar or field effect transistors. The transistors are operated with the linear part of its characteristic and switched in series to the load.

Mains connection

Stated is the mains voltage, the permissible tolerance (±10%), the line frequency range and the type of mains connection, e.g. single phase, two-phase or three-phase. The conductors for N (neutral) and PE (protective earth) are always necessary.

Nominal power

Maximum available power from the power supply. No higher power is available – even for a short time. For FuG power supplies the first number in the type name is the power class or the main component of the the power supply. This value is approximately (but may be not exactly) the nominal power.

Nominal current

Maximum adjustable current.

Nominal voltage

Maximum adjustable voltage. For FuG power supplies the second number in the type name is usually the nominal voltage of the power supply.

Output isolation

On units where the “0V” terminal is not firmly connected to earth (or may be optionally disconnected from earth), it is always shown up to which maximum voltage the terminal may be allowed to float with respect to earth. For units with floating output (all FuG low and medium voltage power supplies up to 2kV – except cassettes) this value is valid for either of the output terminals.


Regulator with Puls Width Modulation. Such regulators are used in switch mode power supplies and in drives.

Power limitation

The output power of FuG autoranging power supplies is limited to a fixed value. All other supply series can be operated at both nominal voltage and nominal current simultaneously.

Power control

Adjustable regulation of output power see options.


FuG name for our system of computer interfaces.

Polarity reversal

for high voltage power supplies a polarity reversal switch is available as an option.


The transition of a super conducting coil / magnet from super conducting to normally conducting condition. If no special measures are provided, the energy, stored in the magnetic field, will be transformed into thermal energy within a short time when this happens.

Quench detector

Circuit for detecting a quench


Accessories to mount table-top units into a 19″ rack. (see also accessories)

Regulations and standards

The design and production of FuG power supplies is in accordance with the latest standards for EMC and safety. See also CE.

Recovery time

This characteristic is stated independently for voltage and current:
For voltage control, it is the time which the power supply requires to return to the adjusted voltage after a load variation from 10% to 100%, or from 100% to 10%.
For current control, it is the time which the power supply requires to return to the adjusted current after a load variation where the output voltage does not change by more than 10% of the nominal voltage.

Repetition frequency

This frequency corresponds to the repetitive charge and discharge of a capacitor by a capacitor charging power supply.


Repeatability of setting of a desired output value under constant conditions – it is always referred to the nominal value of the supply.

Residual Ripple

If not otherwise stated the residual voltage ripple is the referred-to parameter. It is always referred to the nominal value independent of the set value. The frequency of the ripple is the frequency of the mains rectifier and its harmonics. For chopper controlled units there is also a component with the switching frequency (usually 20kHz/40 kHz). For capacitor charging power supplies the value of the charging current is the referred-to parameter.


The energetically equivalent DC value (also effective value) to an alternating voltage. It corresponds to the square root of the integral of squares ( Root Mean Square). At a purely sinusoidal voltage the rms value corresponds to about 36% (1/(2 xv2)) of the value “peak-to-peak”. At a pulse range consisting of narrow peaks (what is the case for the residual ripple of a switched mode power supply) the difference can be considerably larger.

Setting time

The time required before the output value of a power supply reaches the set value.

Sensor connection

For FuG low voltage power supplies, sense lines can be connected to these terminals to measure the voltage immediately at the load and by this to compensate for any voltage drop on the load-lines. The nominal output voltage always refers to the actual output terminals and does not take account of any voltage voltage drop on the load-lines. The compensation of the voltage drop on the load-lines is restricted to a maximum of 5% of the nominal voltage (minimum of 1V) and has to be considered when choosing a supply.

Setting resolution

Smallest possible steps for the adjustment of voltage or current – always referred to the nominal value.

Switch mode power supply

FuG Power supply where the transmission of energy is performed by high frequently alternating voltage.


See deviation.


The design and production of FuG power supplies is in accordance with the latest standards for EMC and safety. See also CE.


See under CE mark.

Temperature range

See Ambient temperature.

Temperature coefficient (TC)

In addition to the value for long-term stability (see deviation), we also refer to the ‘drift’ of an output value as a function of the variation in the ambient temperature whilst the supply is operating under otherwise constant conditions. The data is specified as ‘per Kelvin’ and is only valid within the stated operating temperature range. The TC is always referred to the nominal value. When the option “higher stability” is integrated, then the TC figure improves.

Thyristor regulation

Control of energy flow by a phase cutting circuit with thyristors, operating at the frequency of the mains input.

Trigger input

Capacitor charging power supplies have a potential-free input (opto-coupler) for the control of the charging cycle.

Unipolar power supply

Units with only one polarity and with no regulation through zero.

Voltage control

Standard power supplies can be operated in constant voltage or constant current mode. The switchover occurs automatically with a sharp transition.

2-quadrant operation

The unit operates as a current source and also as current sink (electronic load) with only one polarity of the output voltage. (see active pull-down control)

4-quadrant operation

The unit operates as a current source and also as current sink (electronic load) with both polarities of the output voltage. (see also bipolar power supply)