PoE Cable Tester: Check Voltage at the Cable End
A PoE cable tester reads the voltage present on a live Ethernet link so you can confirm power at the camera end instead of guessing at the rack. A good one shows 5–60 V, tells 802.3af from 802.3at and from non-standard injectors, and checks polarity — so when a camera does not power up you know in seconds whether the fault is the switch port, the cable or the device. This guide covers what to read, how to test safely, and where a budget unit stops being enough.
Every CCTV installer knows the moment: you have mounted the camera, run the cable, plugged it in — and the picture never comes up. Without a way to read power at the far end you are left climbing back down the ladder and walking back to the NVR cabinet to see whether the port is even supplying PoE. Do that a dozen times in a day and you have handed a client free labour.
What a PoE cable tester tells you at the far end
Plugging a PoE tester in at the camera end answers the three questions that actually matter on site:
- Is power present, and how much? A live reading of 5–60 V confirms the port is energised and the voltage has survived the run — long cables and thin CCA can drop it below the device threshold.
- Is it af, at or non-standard? A 15 W 802.3af port will not run a 25 W pan-tilt-zoom camera. Reading the class stops you fitting a device the port can never power.
- Is the polarity right? Non-standard injectors and passive PoE do not always follow the mode you expect; a tester confirms it before you connect the camera.
That is the difference between "the cable's fine, it must be the camera" and a number on a screen. It also settles the most common three-way fault on a job — is it the switch port, the cable, or the camera — without a second trip to the rack.
Budget vs professional: what the extra spend buys
Plenty of installers ask for a "decent but not silly-money" tester — something that does the fault-finding of a Fluke without the Fluke invoice. Here is roughly where the tiers sit in the UK:
| Tier | Typical UK price | PoE capability |
|---|---|---|
| 9V continuity box | £10–£25 | None — continuity only |
| 5-in-1 handheld (e.g. Mcbazel) | £76.27 | 5–60 V, af/at + non-standard, polarity |
| Certifier (Fluke-class) | £300+ | Full PoE + signed reports |
A £40–£50 unit from a name like Noyafa may cover basic continuity and simple PoE indication; the step up to a 5-in-1 buys a live voltage figure, class detection, plus TDR length, fault distance and tone tracing in the same handheld — the features that shorten a fault call, not just confirm a plug is crimped. If you also want the fuller category overview, see our network cable tester buyer's guide, and for wiremap detail the RJ45 cable tester guide.
How to test PoE safely on a live link
- Confirm the tester is set to its PoE/voltage mode before connecting to a live port.
- Connect at the device end of the run — that is where you need to know the voltage actually arrives.
- Read voltage, class (af/at/non-standard) and polarity. Compare against the camera's minimum spec.
- If voltage is low, suspect run length, a poor crimp or thin CCA cable; drop back to a wiremap and TDR check.
- Only mount and connect the camera once the port is confirmed good.
Always follow safe working practices around live equipment and isolate circuits where your employer or the site rules require it.
A one-bag option for install season
Kitting out before the autumn install rush (October to December is when most of this work lands) is exactly when a single do-it-all handheld earns its place. The Mcbazel Advanced 5-in-1 PoE Network Cable Tester reads PoE voltage across 5–60 V for 802.3af/at and non-standard supplies, and adds wiremap, TDR fault distance and tone tracing — so it replaces three tools in the bag. It is £76.27 inc. VAT (£63.56 ex. VAT), free UK next-day delivery, 12-month warranty, and rates 4.7/5 from 342 reviews, many from installers who note the PoE checker saves them "constantly running back to the NVR".
Read power at the camera, not the rack. See the Mcbazel 5-in-1 PoE tester specifications and installer reviews.
Honest limits worth knowing
A handheld PoE tester reads presence, voltage, class and polarity — it is not a load tester and will not certify that a port sustains full wattage under a hot camera all day. It is also not a Cat6 certifier, so it will not print the signed performance reports some commercial contracts require. And it runs on AAA batteries rather than a rechargeable pack, so keep spares for a long day. For day-to-day CCTV and access-point fault-finding, those limits rarely bite; for formal certification, hire a certifier.
Frequently asked questions
Can a PoE cable tester damage my switch or camera?
Reading voltage in the tester's PoE mode is a passive measurement designed for standard 802.3af/at links and common non-standard injectors. Follow the device instructions, connect in the correct mode, and observe your site's safe-working rules around live equipment.
Will it detect non-standard or passive PoE?
Yes. The Mcbazel 5-in-1 reads 5–60 V and covers 802.3af, 802.3at and non-standard supplies, which is important when a camera kit ships with its own passive injector rather than a standards-based switch.
Why does my camera get power on the bench but not on the run?
Usually voltage drop or a marginal crimp. A long run, or thin copper-clad aluminium cable, can pull the delivered voltage below the camera's threshold. Read the voltage at the far end, then check the wiremap and cable length to find the weak link.