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About laboratory power supplies
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What was a laboratory power supply?
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Types and types
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Purchasing criteria for laboratory power supplies – what is important?
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Our practical tip: Safe handling of laboratory power supplies
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FAQ – Frequently asked questions about laboratory power supplies
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Conclusion: This is how you buy the right laboratory power supply
What was a laboratory power supply?
In contrast to simple fixed voltage power supplies and power supplies that only permit voltage regulation, laboratory power supplies (also called laboratory power supplies) also offer the option of setting a current limitation . To set the current and voltage as well as to display these two values with connected load, laboratory power supplies have analogueue or digital volt and ampere meters . The devices consist of a transformer that reduces the supply voltage to a lower value, a rectifier with smoothing and a control circuit .
Voltages and currents can be set separately for each output and from zero or at least almost zero up to the respective maximum values. In general, there are 4 mm connection sockets on the front to which the load is connected. Laboratory power supplies generally have short-circuit-proof outputs, although not all versions are necessarily protected against permanent short-circuit. The outputs are usually switchable, so that the connecting cables do not have to be disconnected or plugged in each time to switch the connected consumers on and off.
Types and types
In the first instance, linear-regulated laboratory power supplies and switching power supplies are distinguished from the electrical design. Her main difference is that it is possible to There are also variants that combine these two techniques. The advantage of linear regulated laboratory power supplies is a very clean, low-interference output voltage as well as a mostly more precise control . However, their space requirements are higher due to the larger transformer, and the weight also increases significantly for more powerful versions. In addition, their efficiency is worse than switched-mode power supplies , which results in a higher effort to reduce the resulting power loss. Laboratory power supplies with switched-mode power supplies are relatively compact and light . Due to the synchronized control, they have an h higher efficiency and generate correspondingly fewer losses and waste heat. The disadvantage may be that – especially at very low voltages – there is not as good regulation as with linear laboratory power supplies and that the output voltage can also be stored in interfering signals from the internal PWM-control.
Complex circuit concepts combine a classic, linear control with upstream switching regulators to increase efficiency while still achieving good control properties and a low-interference output voltage. Such laboratory power supplies are available with high power and are usually equipped with additional functions.
Laboratory power supplies are available with one output as well as in multi-channel versions. Simple devices have analogueue display instruments for voltage and current and potentiometers for voltage and current setting. Intermediate bench power supplies are typically equipped with digital amps and voltmeters, which allow for higher resolution and reading accuracy. In addition, there are almost always additional potentiometers for fine adjustment of current and voltage. So-called sense inputs allow a voltage measurement through additional cables directly at the consumer and thus enable the complete compensation of voltage drops in the connection lines.
Complete digital laboratory power supplies enable the input of the required voltages and currents via a keypad and a corresponding display. Additional functions in the form of power limitation in watts, electronic backup function, tracking function and the possibility to store certain measuring device configurations are often available. Similarly, such laboratory power supplies usually have interfaces that permit remote control and reading of measured values.
Laboratory power supplies with arbitrary function – similar to a function generator – are able to output various programmable signal forms for voltage and current and to realize time sequences. These waveforms can be programd either on the device or via appropriate software, if an interface is available. This makes it possible to remote control the arbitrary function via a test system.
Purchasing criteria for laboratory power supplies – what is important?
First you should consider whether a laboratory power supply with one output is sufficient or different voltages are often required. Laboratory power supplies with multiple outputs not only allow the connection of modules that require different operating voltages, but also offer the possibility of connecting individual outputs together for voltage or current increase. It is advantageous that the voltage and current settings can often be set together if a so-called tracking function is available which allows the individual channels to be linked.
Digital, programmable laboratory power supplies with interface can be used at the most universal and can also be used for automated test sequences. Built-in protection features protect connected consumers from damage when certain predefined limits are exceeded.
The housing design can be a criterion if the space conditions at the place of use play a role. It is also important to know whether multiple devices can be stacked.
Our practical tip: Safe handling of laboratory power supplies
The power supplies are available with voltage outputs that can supply dangerous contact voltages for humans. A series connection of the individual outputs of multi-channel laboratory power supplies can also lead to dangerously high voltages. Only appropriately trained persons are allowed to operate the devices. The relevant safety regulations must be observed and the insulation of the connection cables must be designed for the corresponding voltage.
FAQ – Frequently asked questions about laboratory power supplies
What is the difference between an adjustable power supply unit and a laboratory power supply unit?
Simple, adjustable power supplies only offer the possibility to vary the output voltage in a certain range. A current limitation as with laboratory power supplies is not possible, also its voltage stability is rather limited.
Can multiple outputs be connected in series or in parallel on multi-channel laboratory power supplies to increase the voltage or current?
This is usually possible. Observe the corresponding notes in the operating instructions.
Conclusion: This is how you buy the right laboratory power supply
Make sure that the power values are adequate . Many laboratory power supplies do not provide the maximum current at each output voltage; often derating occurs when a certain voltage is exceeded. It is worth looking at the data sheet to avoid unpleasant surprises later on.
Multi-channel laboratory power supplies are usually economically cheaper to buy than buying several individual power supplies. They require less space and allow central operation and, if necessary, control. If high-quality and expensive modules or systems are to be operated, a laboratory power supply with overvoltage protection (OVP) is recommended. A safety function (Fuse Linking) is also recommended.
Passive cooling, or low-noise, temperature-controlled active fan cooling, ensures a quiet working environment and facilitates concentrated work.
If the laboratory power supply unit is to be integrated into a test system, then the presence or upgradeability of the required interfaces must be ensured. Additional, rear connection sockets and a mounting option for 19" racks prevent cable clutter and allow space-saving storage.
If there are high requirements for a low-interference output voltage and precise control properties, linear-regulated laboratory power supplies are particularly well-placed. Even high-quality versions with electronic pre-regulators and downstream linear regulators generate very clean voltages with low residual ripple and hohem efficiency.