Weight: lbs

Peak Atlas ZEN - Zener Diode Analyser

est Zeners, Avalanche diodes, VDRs, TVSs, LEDs (and LED strings) and more with the new Atlas ZEN. Tests devices up to 50V at selectable currents (2mA, 5mA, 10mA and 15mA).

Displays Zener voltage and slope resistance.

Uses short current pulses to minimise temperature rise even at 50V and 15mA test conditions.

User Guide

Test Zeners, Avalanche Diodes, VDRs, TVSs and much more (up to 50V!)

Atlas ZEN - model ZEN50 - Zener Diode Analyser

Easy, comprehensive and flexible.

Selection of Zener and Avalanche Diodes
Supports most Zeners large and small.
  • Supports most Zeners, Avalanche diodes and reference diodes from 0V up to 50V.
  • Great for testing VDRs, TVSs and other types of voltage protection devices.
  • Selectable test currents: 2mA, 5mA, 10mA and 15mA.
  • Tiny duty cycle of test current to minimise heating of your component even when testing at 50V and 15mA.
  • Measures breakdown voltage (0.00V to 50.00V) with a resolution as fine as 20mV.
  • Measures slope resistance (up to 1kΩ at 15mA with a 1Ω resolution).
  • Single Alkaline AAA battery (included).
  • Long battery life and regulated test conditions even when the battery voltage is as low as 1.0V.
  • Test voltages are below levels described in the Low Voltage Directive 2006/95/EC.
  • Continuous measurement display (updated 3 times per second).
  • Measurement "hold" function to hold displayed values even if component is removed.
  • Fitted gold plated crocodile (alligator) clips.
  • Very comprehensive printed user guide.
  • 24 month warranty.

What's included?
  • ZEN50 instrument.
  • Comprehensive printed user guide.
  • AAA Alkaline Battery.
  • Fitted premium gold plated croc clips.

The Atlas ZEN measures slope resistance intelligently

Slope resistance can be estimated by measuring the change of current due to a change of voltage (see red line), but that assumes that the curve is straight. The result may not always be accurate.

You can get closer to the true slope if you use smaller changes of current. but the measurement resolution can suffer when dealing with small changes and this can also impact on slope calculation accuracy.

The Atlas ZEN derives a curve from 3 points (in blue), differentiates it, and then calculates the slope at the actual point you're interested in (shown in green).

Atlas ZEN can test LED strings too if you take care with polarity.

The Atlas ZEN will test LEDs and LED strings too

If you take great care with connection polarity*, you can test LED strings from just a few volts all the way up to 50V.

In this example shown here, a string of 16 Luxeons (Lumileds) are wired in series to make a 44V string. The Atlas ZEN will happily test the string of LEDs at the selected test current and display both the forward voltage and the slope resistance.

Note however that the current is applied in very narrow pulses, so your LEDs won't be illuminated as brightly as you would obtain for a constant current of the same magnitude.

* Please note: If you connect your LEDs the wrong way round, the voltage generated by the ZEN50 will almost certainly kill your LEDs, you have been warned. If you are not 100% confident about the connection polarity, do not use the ZEN50 to test your LEDs.

Atlas ZEN (ZEN50) and DCA Pro (DCA75) Comparison for testing Zeners
  Feature Atlas ZEN Atlas DCA Pro  
Zener voltage range 0 to 50.0V <12V
Zener test current 2mA, 5mA, 10mA, 15mA <5mA
Zener voltage measurement Yes Yes
Slope resistance measurement Yes -
Curve tracing - Yes
Test Signal Resolution 12 bits 12 bits
Voltage measurement resolution 20mV 20mV
Atlas ZEN50 - Frequently Asked Questions (FAQs)
  Can the ZEN50 be used in-circuit? Not really. Nothing nasty should happen to your Atlas ZEN as it can cope with abuse voltages of ±50V. But your circuit may be exposed to voltages that it is not designed for. Additionally, other circuit effects can influence the ZEN's readings.  
Can I test the VF of diodes and LEDs? Yes. You can even test LED strings with a string voltage of up to 50V with ease. Take great care not to connect your LED(s) in reverse though, the test voltages generated by the Atlas ZEN will exceed the maximum reverse voltage for most LEDs.
What about precision voltage references, will it test those? The Atlas ZEN will apply its test currents in short pulses to your component, it then measures the resulting voltage across it. The test current pulses are kept deliberately short (to prevent temperature rise) so some voltage reference ICs may not respond fast enough. We have tested many however with no problem.
How is the slope resistance measured? The Atlas ZEN automatically tests your device over a span of test currents and internally generates a fitted curve. The curve is mathematically differentiated to calculate the slope at your selected test current. This is more accurate than simply averaging the slope between a pair of test currents.
How much voltage is generated by the ZEN? The Atlas ZEN generates voltages of up to 60V in order to be able to test components that require up to around 50V to operate. Both the voltage and current are electronically limited. The voltages are below levels described in the Low Voltage Directive 2006/95/EC.

Summary specifications (at 25°C unless otherwise specified):






Zener voltage range (Vz)





Nominal test currents (Iz)

2mA, 5mA, 10mA, 15mA


Set test current accuracy

±1% ±0.2mA


Zener voltage measurement accuracy

±1% ±40mV


Zener voltage measurement resolution





Test voltage into an open circuit (pulsed)





Test current into a short circuit (pulsed)





Test current duty cycle





External abuse voltage





Slope resistance measurement range




Displayed Slope resistance resolution




Slope resistance measurement accuracy


±1% ±10Ω
±1% ±4Ω
±1% ±2Ω
±1% ±2Ω



Slope resistance current span

(Iz-50%) to (Iz+50%)


Slope resistance measurement method

Differentiation of curve that fits:
(Iz-50%,Vz1), (Iz,Vz2) and (Iz+50%,Vz3)


Measurement rate





Auto-off period


60 seconds



Battery type

AAA Alkaline x 1


Battery voltage range





Low battery warning

1.0V ± 0.05V


Dimensions (excl. leads)



Operating temperature





Specifications subject to change. E&OE.

1. 60V pulsed DC satisfies lower limit of 75V(DC) for Low Voltage Directive 2006/95/EC.
2. Duty cycle of test current designed to keep power dissipation of Zener under test to very low levels.
Atlas ZEN Document Downloads