Laboratory power supply
As a laboratory power supply , including laboratory power supply called, are power supplies , made up, universal in electronic design , in testing and service area , in the hobby electronic and training can be used.
Laboratory power supplies are available in a wide variety of designs with one or more fixed or adjustable voltage limits, fixed or adjustable current limits and for different outputs, depending on the requirements . Tracking-capable laboratory power supplies can output symmetrical output voltages with different signs but the same amount.
Laboratory power supplies always have a regulation , at least for the output voltage, often also for the output current. They can be designed with a mains transformer , rectifier and linear control or as a switched-mode power supply .
Demarcation
In contrast to conventional plug-in or table-top power supplies, laboratory power supplies have some typical features:
- The output (s) are generally protected against overload, short circuit and polarity reversal .
- Certain types of laboratory power supplies can also function as an electronic load ; H. the laboratory power supply can take up an externally applied power.
- Impulse behavior, ripple and noise of the output voltage (s) are specified.
- A fixed or adjustable current limitation is available; it is an essential distinguishing feature to conventional power supplies: When the set maximum current is reached, these laboratory power supplies change from the behavior of a constant voltage source (with load-dependent current) to that of a constant current source (with load-dependent voltage). The output voltage in the operating range of constant current control is therefore lower than the set limit value. This can go as far as a short circuit without damaging the device because the current is kept at the set value. The diagram shows for a rather low ohmic load (flatter inclined straight line) that the current limitation is active, and for a rather high load (steeper inclined straight line) the voltage limitation. The operating state that is established results from the intersection of the rectangular power supply characteristic with the load characteristic.
- At least in the case of adjustable devices, there are displays for the set or output voltage and the set or output current.
- The connections are standardized, mostly designed for the connection of so-called banana plugs ; in the case of laboratory power supplies that can supply voltages above 60 V, they are usually designed to be safe to touch.
- High-quality laboratory power supplies can be set from a control computer via interfaces such as the IEC-625 bus , or with newer laboratory power supplies using LXI . In some cases, they can also carry out test sequences independently, so that the transition to power signal generators is fluid.
- Higher quality laboratory power supplies often have two additional sockets, which are usually labeled with "Sense" (recognizable in the photo on the lower device). When the load is connected with the usual two supply lines, the built-in regulator keeps the voltage measured at the sockets constant when the voltage is limited. Voltage losses in the plug contacts and supply lines are not recorded and not regulated. However, if the consumer is connected like a low-resistance measuring resistor using the additional measuring (sense) lines in a four-wire circuit , the voltage is measured directly at the load (instead of at the terminals) and kept correspondingly stable. No current flows in the additional lines, so there is no voltage loss.
