HOW TO CALIBRATE HTC-1 HYGROMETER | Using the Salt Method (75% RH Test)

To calibrate your HTC-1 hygrometer using the salt method, you will expose it to a sealed, stable environment of 75% relative humidity (RH). Since the HTC-1 does not have an internal calibration button, you will determine its error offset and mentally (or physically) apply it to future readings. Materials Needed: Table salt Water (distilled water is best, but tap water works) A small, shallow container (like a bottle cap or a small medicine cup) Airtight container or heavy-duty Ziploc bag large enough to hold the salt and the HTC-1 Step 1: Prepare the Salt Solution Pour a small amount of salt (about 1 to 2 tablespoons) into your bottle cap or container. Add water drop by drop. Mix it until the salt has a "wet sand" or "sandcastle" consistency. Important: Do not add too much water. The salt should look damp and clumpy, but there should be no standing water on top. Step 2: Seal the Environment Place the cap of damp salt and your HTC-1 device into the airtight container or Ziploc bag. Make sure the HTC-1 is not touching the wet salt. You can prop it up slightly if needed. Seal the container tightly. Step 3: Wait for Equilibrium Leave the sealed container undisturbed for 8 to 24 hours in an area away from direct sunlight, air conditioning/heating vents, or drafty windows. The salt will create a controlled environment of exactly 75% RH within this trapped air space. Step 4: Check and Record the Offset After the waiting period, check the humidity reading on your HTC-1 without opening the sealed container. A perfectly calibrated device will read 75.0%. Calculate your offset: If your HTC-1 reads 70%, it is running 5% too low. If it reads 78%, it is running 3% too high. Step 5: Apply the Offset Since the HTC-1 lacks a recalibration button, you can simply write your offset on a piece of tape and stick it to the back of the device. Example: If your HTC-1 reads 71% during the salt test (a -4% offset), you will always add 4 to the current reading when checking the room's humidity (e.g., a displayed reading of 50% means the actual humidity is 54%).