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Laboratory Power Supply Buying Guide

Power up your options…

27/08/2020

With a wide range of power supplies available, finding the best model for your department can be challenging. This guide will help you to select the perfect power supply for your needs – referring to key features and comparing key attributes such as the level of education you are teaching, output voltage, current, durability, and cost.

Secondary – Key Stage 3 & 4

Safe, reliable power supplies, which are lightweight and robust. Features short-circuit protection, overload protection with automatic reset, and thermal cut-outs. Regulated DC with a simple rotating switch to select the voltage. 3, 4.5, 6, 7.5, 9, 12V DC. Choice of 1.5A or 3A. [EL190100 & EL190150]

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Compact power supplies offering 2, 4, 6, 8, 10, 12V at currents of up to 5A. Both DC and AC outputs may be used simultaneously up to the rated output. The output is protected by a push button cut-out. The units are 2A fused on the back panel. In the powerlock version the voltage selection is made using a key switch which can be removed. [EL06857 & EL06859]

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Safe, reliable power supplies, which are lightweight and robust. Features short-circuit protection, overload protection with automatic reset, and thermal cut-outs.

Regulated DC with a simple rotating switch to select the voltage. 3, 4.5, 6, 7.5, 9, 12V DC. Choice of 1.5A or 3A. [EL190100 & EL190150]

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DC Output:

  • 0-12 V continuously variable
  • 3 A max
  • Ripple and noise 100 mV max.

AC Output:

  • 2, 4, 6, 12 V stepwise adjustable
  • 3 A max

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The above power supplies offer sufficient power output for experiments in optics, circuit investigations, heat experiments, practical work in the studies of electricity, understanding current and voltage in physics and other applications across the Biology and Chemistry curriculum.

Further Education – Key stages 5

Power supplies for use by teachers and students at A level should have the following features:

  • AC & DC Voltage – Range AC 0-15V, DC 0-20V, 5A min.
  • Continuously variable voltage
  • Digital voltage display (desirable)
  • Overload protection
  • Smooth

This unit supplies 0-20V smoothed DC and 0-16V AC at 8amps. Output is continuously variable and protected by a panel mounted thermal cut out. An output limiter is fitted which allows the user to pre-set the maximum voltage available.

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This power supply is manufactured from sturdy, powder coated steel. Output voltage is continuously variable within the range 0-15V AC or 0-20V smoothed DC, at up to 8A. The unit is short circuit protected and comes with a maximum voltage lock.

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This power supply features independently variable AC and DC outputs with their own voltage and current displays. Both outputs feature electronic overload protection. A DC current limiter is operated through a hole in the front using a screw driver, thereby allowing the teacher to set a current limit.

DC Output:

  • 0-24 V DC continuously variable
  • 10 A max.
  • Display: 1 % ±2 LSD
  • Ripple and noise: <25 mV pp
  • Current limiter

 

AC Output:

  • 0-24 V AC continuously variable
  • 6 A max.
  • Display: 2 % ±2 LSD

 

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Specialist power supplies

This power supply is specially designed for electromagnetic investigations where high current at low voltage is required. The unit will deliver up to 16A AC or DC through its colour coded terminals.

AC & DC Output: Voltages 1-2V
Current 16A
Voltage type: Fixed

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The transformer is a general-purpose low voltage type which can be used to provide power in many applications such as a ticker tape timer, low voltage lamps, heating elements etc.

Outputs
Fixed outputs of 2, 3, 8 and 12V AC are available from four 4mm sockets equally spaced around a central common socket (0V). Outputs are obtained either by tapping between the central common socket and an outer socket, or between two outer sockets. e.g. by tapping between the 2V and 12V sockets a 10V output can be obtained. The maximum current that can be drawn at any voltage is 6A continuously or 8A for periods of up to 1 hour.

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HT (High Tension) Power Supplies

HT power supplies produce an output of at least 300 V at 60 mA or more. This is hazardous and carries a significant risk of an electric shock. CLEAPSS recommends you label them ‘High Voltage Unit. To be used by authorised staff only’.

HT supplies must be used with shrouded leads. These have a retractable plastic sheath, which springs down when inserted into a female jack. HT supplies are used with some electron-beam tubes, some gas discharge lamps, Millikan oil drop apparatus and other experiments requiring up to 300V at low current.

Shrouded leads

Safe, reliable power supplies, which are lightweight and robust. Features short-circuit protection, overload protection with automatic reset, and thermal cut-outs.

Regulated DC with a simple rotating switch to select the voltage. 3, 4.5, 6, 7.5, 9, 12V DC. Choice of 1.5A or 3A. [EL190100 & EL190150]

Find out more 

The transformer is a general-purpose low voltage type which can be used to provide power in many applications such as a ticker tape timer, low voltage lamps, heating elements etc.

Outputs
Fixed outputs of 2, 3, 8 and 12V AC are available from four 4mm sockets equally spaced around a central common socket (0V). Outputs are obtained either by tapping between the central common socket and an outer socket, or between two outer sockets. e.g. by tapping between the 2V and 12V sockets a 10V output can be obtained. The maximum current that can be drawn at any voltage is 6A continuously or 8A for periods of up to 1 hour.

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EHT (Extra High Tension) Power Supplies

EHT (Extra High Tension) power supplies can produce voltages of up to 6KV. EHT supplies contain a 50MΩ internal resistor and the output terminals give the user the option of including this internal resistor within a given circuit.

Without including the resistor in a circuit, the output is current-limited to a maximum of up to 5mA. When the internal resistor is used, the maximum current drawn is much lower 0.1mA, presuming a 5KV output and 50MΩ internal resistor.

EHT supplies are used with some electron-beam tubes, demonstrating supercapacitors, demonstrating electric field lines, spark counters in radioactivity demonstrations plus others.

This 6 kV power supply provides a stable DC voltage for a wide range of experiments. It is short circuit proof and the current limiting series resistor provides reliable protection. The accurate built-in voltmeter eliminates the need for an expensive external voltmeter – making experiments simpler.

DC Output:

  • 0-6 kV stabilised, continuously adjustable
  • 2 mA max.
  • Ripple and noise <1 %
  • Display better than 1% + 1 digit
  • Fully floating output

 

AC Output:

  • 6.3 V fixed, 3 A max.

Continuously variable output from 100V to 5kV. Output voltage is indicated on a 14mm 2-digit LED display. The EHT circuits are fully floating so that for certain applications the positive or negative terminal may be safely connected to earth.

The EHT outputs are taken from 4mm shrouded sockets and provide 100V to 5kV DC up to a maximum of 3mA or current limited to 60µA. A centre tapped socket is provided to give ±2.5kV output.

An additional pair of 4mm shrouded sockets are provided giving 6.3V AC at 2A for filament supplies. There is also a separate earthing terminal.

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 AC and DC stand for Alternating Current and Direct Current.

An AC voltage is where the polarity of the output periodically reverses direction, in contrast to DC voltage where the polarity of the output doesn’t change.

Parts of a power supply

    • Transformer – changes mains input voltage to voltage required
    • Rectification – is the process of converting AC into DC. In a power supply circuit, this is done with diodes. After rectification, the current flows in one direction, but not steadily.
    • Smoothing capacitor(s) – to reduce the amount of AC ripple on the DC voltage
    • Voltage regulation – to provide the required output V

Regulated or Unregulated

A regulated power supply output voltage is not affected greatly by the range of current it is designed to supply.
With an unregulated supply, the voltage tends to drop as the current increases.

Linear or Switch Mode

In linear power supplies, the mains voltage is stepped down by a transformer and rectified for DC output. The output may or may not be smoothed.
In switch mode the mains voltage is changed to a much higher frequency; this is applied to the step-down transformer and rectified to produce a DC output.

Short-circuit protection, overload protection

The output can be protected by fuses, circuit breakers (cut-outs or trips), or electronic circuits to limit the current.

    • Circuit-breaker switches flip when the breaker is activated and are restored by resetting the switch.
    • Thermal circuit breakers do not trip with brief overloads but may take time before they can be reset.
    • Current limiting output protection reduces the output voltage and current when the output is overloaded, keeping the power supply within safe working limits.

Technician’s Choice Practicals

The Irwin Powerbase S10 is ideal supplementary equipment for students to complete the following required GCSE practicals:

  • AQA GCSE Chemistry required practical 3 & 6 – Electrolysis

    Investigating the elements formed at each electrode when different salt solutions are electrolysed

  • AQA GCSE Physics required practical 6 - Light

    Investigate the reflection of light by different types of surface and the refraction of light by different substances

A Timstar bestseller, the Irwin Powerbase V8 is perfect for carrying out AQA GCSE Physics required practical activity 1:

  • Specific heat capacity

    An investigation to determine the specific heat capacity of one or more materials. The investigation will involve linking the decrease of one energy store (or work done) to the increase in temperature and subsequent increase in thermal energy stored.

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