Best TD Meter for HueForge in 2026 (TD1S vs Td-Free)
Updated 2026-06-19 · by Jay
Want a number instead of a guess? Buy the BIQU AJAX TD1S. It's the current finished TD meter — assembled, plug-and-play over USB-C, reads a TD value straight onto HueForge's own scale — and it's the easiest one to get on Amazon. Check the TD1S price on Amazon.
The short version, in order:
- TD1S — for most people. Finished, screened, on Amazon. The default.
- Td-Free — for tinkerers, budget, or WiFi. Open-source kit from Germany, no Amazon.
- TD-1 PCB (~$10) — for DIY on Amazon. Source your own case and solder it.
- Free step test — if you won't spend. The honest baseline, and often enough.
Heads up: this is a research-based buyer's guide, not a hands-on lab test — we haven't measured these side by side. Some links are affiliate links; if you buy through them FilaScope earns a small commission at no extra cost to you. Details on the affiliate disclosure page.
At a glance
| Meter | Price (approx) | On Amazon? | Display | Assembly | Best for |
|---|---|---|---|---|---|
| TD1S | ~$80 | Yes | OLED + USB-C | Assembled | Most people — plug in and read |
| Td-Free | ~€24 PCB / ~€36 built | No (maker only) | WiFi web UI | PCB or assembled | Open hardware, budget, WiFi |
| TD-1 PCB | ~$10 | Yes | None (bare board) | Solder + case it yourself | Tinkerers on a budget |
| Free step test | $0 | — | LED light box | Print the STL | Anyone not measuring much |
Prices move — check the current listing before you buy. TD1S on Amazon · TD-1 PCB on Amazon
First — do you actually need one?
A TD meter measures transmission distance: how far light penetrates a filament before it's effectively blocked. HueForge uses that single number to predict how colors blend across stacked layers — get it wrong and prints come out muddy or banded. (New to this? Start with What Is HueForge TD?.)
Here's what most buyer's guides skip: you don't need a meter to use HueForge. Read TD off a printed step test for free, or pull a published value from FilaScope's TD database. A device earns its place when you're measuring spool after spool, chasing real accuracy, or just done squinting at a light box. Print a few palettes a year? Save the money.
Measuring a lot? A meter is faster and more consistent than the manual route. Here's what to buy.
The meters, compared
BIQU AJAX TD1S — the mainstream pick. The successor to the original AJAX/BIQU TD-1, built by AJAX 3D and BIQU. Sold complete and assembled only: a small injection-molded housing, OLED screen, USB-C, with quick and continuous capture modes. Reference price around $79.99, but prices move — check the live listing. It outputs TD on HueForge's scale with no conversion. Get this one if you want it to just work.
Check the TD1S price on Amazon
Td-Free — the open-source pick. Built by Mawoka: a VEML7700 light sensor and WS2812B LED, WiFi plus USB-C, with a web UI instead of a screen. Firmware is EUPL-1.2, the CAD is CC BY-SA 4.0 — fully open. It runs about €24 as a bare PCB or €36 assembled, and ships from Germany. One independent review (printys.net) clocked it running roughly 0.8 TD low versus a TD-1 — its firmware offset corrects that — and called the build "super easy."
The catch: Td-Free is not on Amazon. You order it direct from the maker — Td-Free on mawoka.eu, source on GitHub (mawoka-myblock/td-free). It reads TD on HueForge's scale like the others. One note: its automatic color capture is still in beta, so don't buy it for that feature yet.
The original TD-1 PCB — for tinkerers. The original AJAX/BIQU TD-1 is discontinued in favor of the TD1S. But the bare BIGTREETECH TD1 PCB still sells for around $10 if you want to source your own housing and assemble it yourself. Same sensor concept; none of the polish.
Check the TD-1 PCB price on Amazon
A naming note: "TD-1" gets used loosely for the whole line. The original TD-1 is discontinued — the current finished device is the TD1S. If a seller just says "TD-1 meter," confirm which one you're actually buying.
One caveat on accuracy
The ±7.5% figure quoted for the AJAX/TD1S family is a maker claim — single-source, not something I've independently verified. The Td-Free deviation above comes from one independent blog. So treat any measured TD, from any of these meters, as a strong starting point you fine-tune against your own prints — not gospel.
The free option that actually works
Before you spend anything, try the baseline these devices compete against: the free HueForge TD step test on MakerWorld. Print the stepped swatch, view it over an LED light box, and read the last bright step — that's your TD. No hardware cost. It's slower and more error-prone than a sensor, but it's genuinely usable, and it's how plenty of HueForge prints get made. The full method is in our complete guide to measuring TD.
If you'd rather skip measuring entirely for now, the TD simulator lets you preview how different TD values blend, and a ready-made starter set ships with TD values already known.
Bottom line
Most people should buy the TD1S — it's finished, it's on Amazon, and it removes the guesswork. Choose Td-Free if open hardware and a web UI matter more than convenience. Grab the $10 PCB if you like to build. And if you're not measuring much, the free step test is a real answer, not a cop-out.
Once you've measured your spool, drop the value into the TD database — it pairs every TD with the current best price, so the next palette is cheaper to build than the last.