Passmark Inline PSU Tester

The Passmark PM123 Inline PSU Tester enables diagnostics and troubleshooting for desktop PC power supplies.


In Stock, Delivery time: 1 - 3 days

Further information

BurninTest Software V10
Version: Windows | Licensing: Single user
BurninTest Software V10
Version: Windows | Licensing: Single user
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Product number: PM123
Manufacturer: Passmark


The Passmark Inline PSU Tester allows you to diagnose and troubleshoot desktop PC power supplies. Quickly verify that supply voltages are within allowable limits, measure and verify timings such as power-on time and power_OK delay, and test "inline" while connected to your motherboard.


  • The most comprehensive PSU tester on the market
  • Check that the supply voltages are within the permitted limits.
  • Record minimum and maximum voltage and current for each rail.
  • Measure the exact power consumption for each rail.
  • Measure the total power consumption of the PSU.
  • Main voltage rail ripple check
  • Measure and check the turn-on time (T1), rise time (T2), PWR_OK delay (T3), and turn-off warning (T6) and compare them to specifications.
  • Measurement of the minimum slew rate of the main voltage rails at power-up
  • Measure whether the turn-on edge of the main voltage rails is positive during turn-on.
  • Check the power supply order
  • Connects the PSU tester to the PC to monitor PSU statistics and export data to a report
  • Can run in inline or standalone mode

Free PC PSU Monitoring Software

Connect the PSU Tester to your PC via the USB port and you can monitor PSU statistics including voltage, current, power, ripple and timing for each voltage rail.

The readings are clearly displayed with a green background when the value is within the acceptable range and a red background when the value is out of the acceptable range.

Up to three testers can be monitored from one instance of the software and all data can be exported to a text file report.


Why test PSUs?

A faulty PSU can often be the cause of problems you don't expect, such as random hangs, spontaneous reboots, and even some serious error messages

The PassMark PSU Tester was developed to test a PC power supply quickly and comprehensively.

PSU Tester Screen

Information screen

The various information screens can be viewed by scrolling with the buttons on the unit.
Check that the supply voltages are within acceptable limits, measure the exact current draw from each rail and the total power drawn from the supply.

Check for ripple on the main voltage rails, measure the minimum slew rate on the main voltage rails during power up.


The PSU Tester can be used inline with a connected PSU and full load
A PC can be connected via USB to monitor the PSU tester in inline mode.
The PSU tester can also be used in standalone mode.
A PC can be connected via USB to monitor the PSU tester in standalone mode.
Multiple devices can be used simultaneously to test systems with up to 3 GPUs or 2 CPUs. These can be monitored from an instance of the software.


Remove anything conductive from your hands (such as metal rings, watches, or bracelets) before testing a power supply or working inside your computer.
Only use the original cables that come with the tester. The PCIe cable that comes with the tester is not a standard cable and is custom-made for the tester. Using other cables may cause a short between the voltage rails.
Make sure all cables are fully inserted. A loose connection will result in higher electrical resistance which, under high loads, can melt the wires (or even cause a fire).
In the event of a dramatic failure of the device under test, you may see smoke emanating from the power supply or the case rise or smell burning odor. In this case, unplug the AC adapter from the outlet. Under these circumstances, do not touch the power supply or the PSU tester.
Always have someone supervise the test in case the device under test suddenly fails. Don't start a test and don't walk away.
If the PSU tester is inline (i.e. connected to both the PSU and the motherboard), do not turn it on using the tester's keyboard. Use the PC power button instead. This is just a precaution against poorly designed power supplies that don't conform to ATX standards and can prevent a short circuit on the PS_ON line.

When the PSU tester is inline (connected to both the PSU and the motherboard), do not turn it on using the tester's keypad. Use the PC power button instead. This is just a precaution against poorly designed power supplies that don't conform to ATX standards and can prevent a short circuit on the PS_ON line.

First, check that all cables are properly connected and fully seated.
Make sure the "SATA In" cable is plugged in and oriented correctly.
Make sure you are connecting the PC use the "standby" button on the computer case to turn it on, not the keyboard.
If the problem persists, disconnect all cables from the motherboard and force the keyboard to turn on to resolve the issue.

The background color of the PASS/FAIL messages can be green, red, bright red and yellow. Each color has a different meaning, explained below:

PASS means the voltage is currently within acceptable limits and has never been outside specifications.
PASS means that the voltage is currently within acceptable limits, but an overvoltage was previously detected.
PASS means that the voltage is currently within acceptable limits, but an undervoltage was previously detected.
FAIL means the voltage is outside acceptable limits.

This means that the USB 2.0 loopback connector reported a device transceiver error. Device transceiver errors are raised when the USB 2.0 loopback connector's USB transceiver detects an error that it considers to be an error. These are low-level events that can result in the packet being retransmitted. They do not represent application-level data errors. These errors are typically not visible to the user, but are displayed to identify potential problems, such as: Poor quality cables, cables that are too long, or system internals with insufficient electrical shielding and strong electrical interference on the bus. Errors that can cause a transceiver error are:

  • Bad PID
  • CRC error
  • Bit stuff error
  • Extra bits in a packet
  • Full speed EOP ends in K
  • Loss of high speed before EOP (packet truncated)
  • Overflow (host clock is running too fast or device clock is running too slow)
  • Token larger than 3 bytes (this can occur when using the USB 2.0 loopback connector behind a hub and low or full speed devices are connected to the hub).
    Note that device Transceiver errors are not an indication that the USB port does not comply with the USB specification.

We recommend running the BurnInTest on the motherboard during the inline test to increase the power consumption of the motherboard and put more stress on the PSU. 

Rail+12V1+12V2 (12V CPU)+12V PCIe+5V+3.3V+5VSB+12V SATA+5V SATA+3.3V SATA
Max Power300W600W360W150W99W40W66W27W18W

The above figures refer to a hypothetical 1600W PSU. In practice, however, most systems don't draw nearly as much power on each of these rails. When a desktop computer system draws more than 700W, it's usually because it has multiple high-end graphics cards installed (requiring multiple PCIe rails in this case). See also the question below about testing multiple GPUs.

"N/A" means that some of the timings have not been measured yet. The timings are calculated during the switching on and switching off process. So if it shows "N/A" it means it takes a power cycle or two to calculate the timings.

The in-line power supply tester samples the voltage on each rail at 10K samples per second. It then takes 1 second of data, looking for each rail's absolute minimum and maximum voltage every second. The min/max difference is specified as residual ripple. The accuracy of the voltage measurement in our tester is +-4 mV, so that a small residual ripple (around this 4 mV) leads to measurement errors due to quantization errors in the A/DC.
Please note: The measurement of the residual ripple is not precisely defined in the ATX standard. The lack of a defined specification leads to different test methods and thus to different results. The ATX standard states that the ripple should be measured at a bandwidth of 20MHz using a 0.1uF ceramic capacitor and a 10uF electrolytic capacitor to simulate system loading. The PSUTester meets these specifications.

No. The PSU tester can be powered via the 24-pin connector. However, the voltage reference and protection circuits in the PSU tester rely on the 5V input voltage. So if the +5V rail doesn't provide a clean and accurate voltage, it could affect the accuracy of the measurements and the functionality of the protection circuits. For this reason, we recommend connecting the USB port to a PC or a wall charger.

Yes. Measuring efficiency is all about accurately measuring input power and output power. The PSU tester can measure the output power. A quality power meter is also required to measure input power.

In standalone mode, the tester draws 4 watts of power (to load the power supply with a test load). This can cause the base of the tester to feel warm after a short time. To avoid overheating, the tester automatically switches off the test after 1 minute.

The 24-pin input cable should always be connected to provide the ground reference required for voltage measurement. Connecting other cables without a ground reference may damage the tester. The only exception is when the PCS tester is used to test a device with more than one GPU. See "Can machines with multiple GPUs be tested?" below.

Under the Documentation section is a guide that explains how to test computers with multiple CPUs/GPUs.

The test device has a PCIe 6+2 output. However, with high-end GPUs that have dual ports, you can use a Y-splitter. 16AWG is the preferred gauge wire (instead of 18AWG) and the wire should be made of High Current (HCS) pins. It is also important that all connectors are fully inserted to minimize electrical resistance.

A 6-pin PCIe cable delivers 75 watts and an 8-pin can deliver 150 watts, so splitting the cable doesn't seem like a good idea. But before we draw that conclusion, let's do some calculations.
The PCI-E connector has 6 pins. They are not all used for power. With a 6-pin connector, pins 1 and 3 are connected to 12V and can each carry 8A of current. Pin 2 is not connected by default, although most PSU manufacturers add a 12V line there. Pins 4 and 6 are common returns. Pin 5 is ground for the sensor. Using 2 lines with standard pins gives 12V*8A*2= 192 watts, so the actual limit is much higher than the artificial limits (75 watts). As of March 2005, Molex pins must be "HCS" rather than "Std", each capable of carrying a maximum of 11 amps. So a properly made 6-pin PCI-e cable can provide 12V*11Amps*3 lines=396 watts of power for the graphics cards. The output cable that comes with the tester consists of plus HCS pins with 16AWG wires and is rated for 13A. So assuming decent quality cables are used and there are only 2 live 12v lines, you can use a splitter with high end dual connector GPUs for short term use. Quality splitters are safe to use when there are three live wires in the power supply cord.

The log file contains the readings of voltage, current, power, and ripple of various power rails at user-configured time intervals (1, 10, 30, and 60 seconds). An example of the log file can be found here. The report file includes voltage, current, power, ripple and timings for each power rail. The report also includes overall power supply performance and an overall voltage and timing rating (pass/fail). Here is an example report file.

For Windows 7 and 8 you need a device driver. For Windows 10, using the native inbox driver (Microsoft driver) is recommended.

Unfortunately there is currently no Linux driver and no API/SDK.

This is a known issue that occurs when updating firmware from version 1.0 to 1.3. The following steps will help you fix the problem.
- Connect the tester to a PC using the USB cable.
- Launch the PSUTest software
- Click on "Calibration" to start the to open the calibration window
- Click on "Reset all calibration data".
- Click on "OK" to close the calibration window
- Disconnect and reconnect the device


PSU Inline Tester Demonstration
PSU Inline Tester Introduction

Technical Data

Device Comparisongeneric-psu-tester
Common PSU Tester
Passmark- PSU-inline-tester-transparent
PassMark Inline PSU Tester
Voltage measurement
Power and current measurementX
Check the main power rails for rippleX
Measure and verify slew rate (ramp speed)X
Checks the timing (T1, T2, T3, T6)X
Check power-on propensity (smooth power-on)X
Check performance sequencingX
Standalone mode (no motherboard connection)
Inline mode (tests PSU under full load, connected to motherboard)X
USB port (for monitoring)X
PC (Windows) monitoring softwareX
Cables suppliedX
Comprehensive User GuideX
Technical SupportX
Multiple GPU support *X
Model specificationPassmark- PSU-inline-Tester-transparent
PSU Inline Tester
Product codePM123
ProcessorARM Cortex M4
Reminder32 KB RAM, 128 K Flash
User Interface1.8" LCD 128X64 pixels + membrane keyboard
Ports24-pin in, 8-pin CPU in, 6-pin PCIe in, SATA in, 24-pin out, 8-pin CPU out, 6-pin PCIe out, SATA out
Internal loadInternal load (1Watt) on +12V1DC, +12V2DC, +5VDC and +3.3VDC power rails. Active only when the PSU tester is in standalone mode (disable in inline mode).
What can be measuredVoltage:
+12V1DC, +12V2DC (12V CPU), +5VDC, +3.3VDC, +5VSB, -12VDC, +12VDC PCIe

+12V1DC, + 12V2DC (12V CPU), +5VDC, +3.3VDC, +5VSB, +12VDC PCIe, +12VDC SATA, +5VDC SATA. +3.3 VDC SATA

+12V1DC, +12V2DC (12V CPU), +5VDC, +3.3VDC

Power on time (T1 ), rise time (T2), PWR_OK delay (T3) and shutdown warning (T6)

Minimum slew rate and rise:
Check the smooth and continuous rise of +12V1DC, +12V2DC (12V CPU), +5VDC, +3.3VDC.

Power Sequencing:
Check +12VDC and +5VDC against +3.3VDC during power up to ensure they are equal to or greater than +3.3 VDC.
Voltage measurement range+12V: 0 to +14.7V, resolution: 3.5mV
+5V: 0 to +6.6V, resolution: 1.6mV
+3.3V : 0 to +4.5V, resolution: 1.1mV
-12V: -15V to +3.3V, resolution: 4.4mV
Maximum inline current+12V1DC: 25A
+12V2DC (12V CPU): 50A
+5VDC: 30A
+3.3VDC: 30A
+5VSB : 8A
+12VDC PCIe: 30A< br>+12VDC SATA: 5.5A
+5VDC SATA: 5.5A
+3.3VDC SATA: 5.5A
Operating Voltage5V via USB connector or +5V on 24-pin connector
Operating Current200mA
Measurement error (A)±4% before calibration, 1.5% after calibration (Note 1)
Measurement error (V)±1% before calibration, 0.25% after calibration (Note 1)
Logging and test reportRecords voltage, current, power and ripple at configurable time intervals (1, 10, 30 and 60 seconds).
A report can be generated at any time during the test containing voltage, current, power, ripple and timings for each power rail. The report also includes the total power drawn by the PSU and an overall pass/fail result for voltages and timings.
caseHigh impact ABS plastic
Size225mm x 85mm x 30mm
(8.8 x 3.3 x 1.2 inches)
Weight240g (8.4oz)
Security PrecautionsOvervoltage protection
+12V: protected up to 22V
+5V: protected up to 10V
+3.3V: protected up to 6.5V< /td>
Storage temperature-30 °C to + 80 °C
Usage temperature0 °C to 40 °C
RoHS (lead free)Yes

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