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The widest published range here, and no accuracy at all

Gain Express HTM-238

A handheld meter reading 0 to 100% humidity and −30 to 70 °C (-22 to 158 °F), with Max/Min, hold and a backlit display.

Gain Express handheld digital humidity and temperature meter with backlit LCD

Gain Express HTM-238

A handheld meter reading 0 to 100% humidity and −30 to 70 °C (-22 to 158 °F), with Max/Min, hold and a backlit display.

Humidity range
0 to 100% RH
Temperature range
−30 to 70 °C (−22 to 158 °F)
Readings
MAX / MIN, with a freeze function
Display
Dual large display with backlight
Controls
Two buttons; °C/°F; auto shut-off when idle
Stated uses
Agriculture, meteorology, household, lab, warehouse, air conditioning, quality control
Accuracy
Not stated by the maker
Refresh rate
Not stated by the maker
Amazon reference
B07GXLYF64
EAN
0600316548908
  • The widest published measurement range on this shelf: the full 0 to 100% RH and −30 to 70 °C (-22 to 158 °F)
  • MAX/MIN with a freeze function, which only the two professional instruments here also offer
  • No accuracy published, on a device whose selling point is its range

Best for: Walking round a warehouse, greenhouse or crawl space taking spot readings

≈ $22
Check price on Amazon

Specifications

Humidity range
0 to 100% RH
Temperature range
−30 to 70 °C (−22 to 158 °F)
Readings
MAX / MIN, with a freeze function
Display
Dual large display with backlight
Controls
Two buttons; °C/°F; auto shut-off when idle
Stated uses
Agriculture, meteorology, household, lab, warehouse, air conditioning, quality control
Accuracy
Not stated by the maker
Refresh rate
Not stated by the maker
Amazon reference
B07GXLYF64
EAN
0600316548908

What the maker puts in writing

  • 0 to 100% RH · −30 to 70 °C (−22 to 158 °F)
  • MAX / MIN readings with freeze
  • Dual large display with backlight
  • Two buttons, °C/°F, auto shut-off

The range is the claim

The full humidity scale and a hundred-degree Celsius span. No other device on this shelf publishes a range that wide, and two publish none at all.

For a warehouse or a crawl space that is the right shape of instrument: you carry it, you hold the reading, you move on.

And the number it does not give

How close is it. On a meter sold for quality control and lab use, the tolerance is the specification, and the listing substitutes “high precision sensor” for it.

A twenty-dollar hygrometer on this shelf publishes ±0.54 °F and ±3% RH, logs for twenty days and survives rain. For the same money, that is a documented instrument against an undocumented one.

Availability

Read on the day this page was built: $22 at the American Amazon shop.

Read from Keepa on the day this page was last revised; stock and price both move without notice.

Prices quoted in this text were read on 2026-10-04. The live price is at the top of the page.

The questions that keep coming up

Does the wide range help me?

Only if you need it. Zero to a hundred per cent and −30 to 70 °C (-22 to 158 °F) covers a freezer and a greenhouse; a living room sits in the middle fifth of that. A narrower, documented range is more useful indoors — and the TempPro and GoveeLife on this shelf publish tolerances instead.

How accurate is it?

Not published. "High precision sensor" and "high stability readings" appear in the listing with no figures behind them. Four devices on this shelf give tolerances; this is not one of them.

What is the freeze function for?

It holds the reading on screen so you can write it down while moving away from the point you measured. Together with MAX/MIN it is what separates a survey tool from a display, and three devices on this shelf have it.

More thermo-hygrometers

  • GoveeLife 2-in-1 indoor outdoor thermo-hygrometer with lanyard and LCD display

    GoveeLife H5171011

    An indoor-outdoor thermo-hygrometer accurate to ±0.54 °F and ±3% RH, rated IP65, with twenty-day curves and app alerts.

    Accuracy
    ±0.54 °F / ±3% RH
    Sampling
    Every 2 seconds
    Protection
    IP65 — rain and moisture, dustproof and sun-resistant; not for immersion
    Weight
    2.39 oz
    Battery
    Up to one year in Bluetooth mode
    Alerts
    Preset temperature and humidity thresholds, pushed to the app
    Data
    20-day curve readings; 2 years of free storage and export
    Mounting
    Nylon lanyard with adjustable buckle; hangs indoors or out
    Display
    LCD with a humidity comfort indicator, no ghosting
    Gateway
    Connects to GoveeLife gateways for remote monitoring
    Amazon reference
    B0FLQD2PC9
    EAN
    0810127738966
    • The tightest published accuracy on this shelf — ±0.54 °F and ±3% RH — and the fastest sampling at two seconds
    • The only device here with an ingress rating, IP65, so it works on a patio or a backpack
    • The alerts and the history need the app: on the device itself you get the current reading and a comfort icon

    Best for: A patio, greenhouse or backpack, or any room where you want the history rather than the moment

    ≈ $21
    Check price on Amazon
  • General Tools RHMG650 9-in-1 thermo-hygrometer and moisture meter with backlit LCD

    General Tools RHMG650

    A nine-function instrument combining a thermo-hygrometer with a pin and pinless moisture meter, recalling twenty reading pairs.

    Measurements
    9, including humidity, dew point and vapor pressure
    Moisture meter
    Pin and pinless
    Temperature range
    −20 to 167 °F
    Memory
    Recalls 20 reading pairs
    Display
    Large backlit LCD
    Accuracy
    Not stated by the maker
    Refresh rate
    Not stated by the maker
    Calibration
    Not stated by the maker
    Amazon reference
    B00I140G2E
    EAN
    0681035016084
    • The only instrument on this shelf with a pin and pinless moisture meter, which reads moisture inside timber and plaster rather than in the air
    • Publishes dew point and vapor pressure, which only one other instrument here does
    • Two bullets: no accuracy, no humidity range, no refresh rate, no calibration statement

    Best for: Building and restoration work, where moisture in a material matters more than comfort in a room

    ≈ $220
    Check price on Amazon
  • LittleGood 6-inch analog wall thermometer and hygrometer with white ABS case

    LittleGood HMTMHY-WT

    A 5.9-inch analog dial reading −30 to +50 °C (122 °F) and 10 to 100 per cent humidity, with a calibration screw on the back.

    Type
    Analog — no batteries
    Dial
    5.9 in / 15 cm diameter, large black numerals
    Temperature
    −30 to +50 °C (122 °F) / −20 to +120 °F, accuracy ±2 °C (36 °F) / ±3.6 °F
    Humidity
    10 to 100%, accuracy ±5%
    Calibration
    Adjustment screw on the back for the temperature
    Scales
    Both Fahrenheit and Celsius, color-coded dial
    Mounting
    Supplied stand, or wall mounting hole
    Case
    White ABS
    Refresh rate
    Not applicable — analog
    Amazon reference
    B09P37W7CY
    EAN
    0613965381178
    • The only analog instrument on this shelf that publishes both tolerances and includes a calibration screw
    • A 5.9-inch dial with large numerals, readable across a room, which no digital display here matches for size
    • ±2 °C (36 °F) is the loosest temperature tolerance published on this shelf

    Best for: A wall in a garage, porch or workshop, read from across the room, with no battery to change

    ≈ $14
    Check price on Amazon

Elsewhere in the spares drawer

  • LOVIGA portable AC window vent kit in white fabric with drawstring hose opening

    LOVIGA US-WdSl-25162

    A fabric window seal 10 inches wide and adjustable from 40 to 64 inches, with a drawstring that closes around any hose from one to six inches.

    Type
    Fabric seal, not rigid plates
    Size
    10 in wide × 40 to 64 in long, adjustable
    Hose opening
    Drawstring, closing on any hose from 1 to 6 in
    Windows
    Horizontal or vertical sliding windows only, single-hung and double-hung
    Fabric
    Waterproof TU fabric with a heat-insulating whitening process to reflect sunlight
    Fixing
    Tape on the window frame, widened Velcro, double-stitched seams, Velcro ties for the hose
    Installation
    Open the window about 7.9 in; no drilling
    Before use
    Leave 24 hours after installation, as stated by the maker
    Warranty
    1 year, with 24-hour customer service
    Amazon reference
    B09ZHFT6LW
    EAN
    0701213188805
    • The drawstring closes on any hose from one to six inches, so the diameter problem that divides the hose shelf simply does not arise
    • The only kit on this shelf with a published warranty — one year — and the only one with numbered installation steps
    • Fabric rather than plates: it has to be taped to the frame and it is less rigid than PVC

    Best for: A rented flat, or any window where drilling is out and the hose diameter is awkward

    ≈ $17
    Check price on Amazon
  • TKOBAIV portable air conditioner window vent kit with plates and exhaust hose

    TKOBAIV 5.9inch

    Four PVC plates adjustable from 16.93 to 63 inches with a 5.9-inch exhaust hose and adaptor included.

    Plates
    2 fixing plates and 2 adjustable plates, 43 cm (16.9 in) / 16.93 in each
    Adjustable range
    16.93 in to 63 in
    Hose
    5.9 in / 15 cm diameter
    Adaptor
    5.9 in / 15 cm exhaust hose adaptor
    Fixings
    3 screws
    Material
    High-quality PVC, anti-aging and anti-squeezing
    Windows
    Almost all vertical and horizontal sliding windows or doors
    Thread direction
    Not stated by the maker
    Screen or filter
    Not stated by the maker
    Amazon reference
    B0GSS9BLX9
    EAN
    0747759789106
    • Includes the hose and the adaptor as well as the plates, for twenty-one dollars
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    • Three screws for four plates, by its own contents list

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    Check price on Amazon
  • ALITOVE universal 5V 1A power adapter with 8 interchangeable connector tips

    ALITOVE Universal 5V 1A Power Adapter (8-Tip)

    A generic 5V DC power adapter rated up to 1A (5W), sold with 8 interchangeable connector tips to match different barrel-plug sizes. This is a universal-fit accessory, not one built for a specific reviewed model — the voltage, current and polarity printed on your original adapter's label are what actually determine a safe match, not the appliance's brand or size. Confirmed with a single live offer on Amazon.de; we did not find a listing on the other three markets we checked.

    Output
    5V DC, up to 1A (5W)
    Connector
    8 interchangeable barrel-plug tips included
    Fit type
    Generic / universal — voltage and polarity match required
    Input
    100-240V AC, per the listing
    • Confirmed with a live offer on Amazon.de
    • 8 interchangeable tips cover several common barrel-plug sizes without buying multiple adapters
    • 5V/1A only — not a fit for any appliance on this site needing a higher voltage or current, which must be checked on the original adapter's label first

    Best for: A small, low-power device — most commonly an air-quality monitor or a small humidifier accessory on this site — that specifically takes 5V/1A and whose original adapter has failed, confirmed against the original's printed label first.

    Search Amazon for this model

All thermo-hygrometers