Network Cable Tester: What It Does and How to Choose One
A network cable tester checks that an Ethernet run is wired correctly and, on better units, measures cable length, locates a fault to the metre, and confirms whether Power over Ethernet is present. If you have outgrown a blink-light continuity box, a 5-in-1 handheld adds the four things that actually save time: wiremap with fault type, TDR length and fault distance, PoE voltage detection, and tone-and-probe tracing. This guide explains each function and how to choose one without paying certifier money.
If you run a homelab, you probably started the same way most of us did: a cheap 9V-battery tester that flashes eight LEDs and tells you almost nothing when a link misbehaves. It confirms continuity and that is it. The moment you start pulling Cat6 to garden cameras, feeding PoE access points in the loft, or wondering why a run negotiates at 100Mb instead of gigabit, that little box runs out of answers.
What a network cable tester actually measures
The term covers everything from a £12 continuity checker to a £300+ certifier. In between sits the category most home and trade buyers want: a multifunction handheld. Here is what each core function does in plain terms.
Wiremap and continuity
A wiremap test sends a signal down each of the eight conductors and reports what returns at the far end: OK, open, short, crossed or split pair. Link lights lie — a crossed pair or a high-resistance crimp can still show green while throughput collapses — so a proper pin-by-pin wiremap is the single most useful check you can run.
TDR length and fault distance
Time Domain Reflectometry sends a pulse and times the reflection, converting it to a distance. That tells you a run is, say, 43 m long, or that a break sits 12 m from where you are standing — the difference between re-crimping a plug and opening a wall. Mcbazel's 5-in-1 quotes a range up to 200 m; treat headline ranges with healthy scepticism and read the honest boundary below.
PoE voltage detection
A continuity test cannot tell you whether power is reaching a device. PoE detection connects to a live switch port and reads the voltage present, covering 5–60 V across 802.3af/at and non-standard injectors. This is the check that separates "the cable is fine" from "the switch port is not powering up".
Tone tracing and port flash
An integrated tone generator and probe let you find one unlabelled cable in a bundle, and a port-flash function blinks the matching switch port so you can identify a run at the rack without unplugging anything.
Do you actually need to upgrade from a cheap tester?
This is the honest question every homelab buyer asks: is it worth the extra over the £40 one? A basic continuity box is fine if you crimp the odd patch lead and never touch PoE. Upgrade when any of these are true:
- You run PoE cameras, doorbells or access points and need to read actual voltage, polarity and whether a link is af, at or non-standard — not just guess by swapping ports.
- You want to build a record of every run in the house: length, wiremap and route, so the next fault is a two-minute job.
- Your runs go through walls, lofts or conduit where re-pulling a cable to find a break is the expensive option.
That second point is exactly why hobbyists graduate from the "cheapo 9V battery tester" — you stop swapping cables and ports on a hunch and start reading numbers.
How to choose: what to compare
| Feature | Budget continuity box | 5-in-1 handheld |
|---|---|---|
| Wiremap | LEDs, pass/fail | LCD, names the fault type |
| TDR length & fault distance | No | Yes, single-ended |
| PoE voltage (5–60 V, af/at/non-standard) | No | Yes |
| Tone trace + port flash | No | Yes |
| Cat5e / Cat6 / Cat6a | Sometimes | Yes |
| Typical UK price | £10–£25 | £76.27 |
For deeper dives on individual functions, see our guides on reading an RJ45 cable tester wiremap, how to test an ethernet cable and find a break in the wall, and using a PoE cable tester at the camera end.
A homelab-friendly option
The Mcbazel Advanced 5-in-1 Network Cable Tester bundles wiremap, TDR length and fault distance, PoE voltage detection, switch port flash and NCV tone tracing in one handheld, and ships with an IEC C13 power cable. On the product page it is £76.27 inc. VAT (£63.56 ex. VAT), with free UK next-day delivery and a 12-month warranty. It rates 4.7/5 across 342 reviews — several from installers who say it rivals far more expensive brands for everyday fault-finding.
Outgrown your continuity box? See full specifications and reviews for the Mcbazel 5-in-1.
Honest limits worth knowing
No handheld at this price is a certifier: it verifies wiring and finds faults, but it does not produce the signed Cat6 performance certificates some commercial contracts demand. TDR distance is an estimate — accuracy drops on very short patch leads and varies a little with cable type and twist rate, so use it to get close, then confirm by eye. And this kit runs on AAA batteries rather than a USB-C rechargeable pack, so keep spares in the bag for a busy day. For most homelabs and small installs, none of that is a dealbreaker; for signed certification, hire a certifier for the day.
Frequently asked questions
What is the difference between a network cable tester and a certifier?
A tester verifies wiring and finds faults (wiremap, length, PoE, tracing). A certifier measures cable performance against a standard and prints a pass/fail report for structured-cabling contracts. Certifiers cost several hundred pounds; most home and SME work only needs a good tester.
Will it work on Cat6 and Cat6a?
Yes. Wiremap, TDR and PoE functions work across Cat5e, Cat6 and Cat6a. RJ45 pinouts are identical across the categories, so one tester handles them all.
Can it read Power over Ethernet from my switch?
Yes. Connect it to a live PoE port and it reads the voltage present across 5–60 V, covering 802.3af, 802.3at and non-standard injectors, so you can tell a powered port from an unpowered one before mounting a device.