Calibration, Batteries and Replacement of Home Health Devices

What calibration means at home

In a laboratory, calibration means comparing an instrument against a known reference and adjusting it. Most home devices cannot be adjusted by the user, and trying to open one up is unwise. What a family can do is check the device against a trusted reference at intervals and replace it if it is off. Think of it as "verification". Many makers recommend professional checks every year or two for blood pressure monitors; others say the device is not designed to be serviced and should be replaced when it fails. Read the manual and ask the seller what service is available.

A routine schedule

• Every use: look at the display; check for low-battery warnings, error messages or odd values.
• Monthly: inspect cuffs, tubes, probes, strips, clips and scale feet; wipe clean; check batteries.
• Every six to twelve months: compare the device with a trusted reference as described below.
• After a drop, water damage or sudden odd readings: check at once.
• Every few years or as the maker advises: replace parts, or the device.

Write the date of purchase and each check on a label inside the device box. See a home health monitoring starter kit.

Blood pressure monitors

Accuracy check. Take the monitor and your parent to the doctor's clinic or a pharmacy with a validated device. Ask a nurse to take readings using the clinic's device and your monitor, on the same arm, a minute apart, in the same sitting and posture, a few times. Differences of up to about 10 points are often accepted; a larger or consistently one-sided difference should be discussed with the doctor. Some clinics can connect a monitor to a reference device to test it, or the maker or service centre may offer a check.

Cuff and tube. Look for leaks, cracked tubing, a worn Velcro that no longer grips and a cuff that does not inflate smoothly. A hiss or slow inflation suggests a leak. Replace the cuff, using one made for your model. Check the size again if your parent's weight has changed; see cuff size and blood pressure accuracy.

Batteries. Weak batteries cause error messages and unreliable readings, sometimes before the low-battery symbol appears. Replace all batteries together, using the type the maker recommends, and take them out if the monitor will not be used for months, so they cannot leak. Keep spares.

Signs it is time to replace. Inconsistent readings in the same sitting, readings far from clinic ones, frequent errors, a damaged display or a cuff that cannot be replaced. Many makers suggest a lifespan of several years of regular use.

See also the blood pressure monitor buying guide.

Glucometers and strips

Control solution. The maker usually provides a liquid with a known glucose level. Use it when you open a new vial of strips, when the meter is dropped, when readings seem wrong or when your doctor asks. If the result falls outside the range printed on the vial, do not use the strips or meter until the cause is found.

Compare with the lab. Test with your meter at the same time as a lab fasting sample, and compare. Meters generally aim to be within about 15 per cent of the lab value, though it is not exact. A big or repeated gap deserves discussion with the doctor.

Strips. Check the expiry date and the "use within" period after opening, keep the vial tightly closed and store away from heat and damp. Never use old, discoloured or open-for-months strips. See glucose strips and lancets: storage, expiry and cost.

Meter body. Keep the strip port clean and dry; do not blow breath into it. Replace the battery when low. Replace the meter if it gives inconsistent results or fails control tests.

Coding. If your meter needs a code for each new vial, check it matches. See glucometers: how to choose and use one.

Thermometers

Digital stick. Compare it with another thermometer or at the clinic. In a healthy person at rest, two good thermometers should agree within about 0.2 to 0.5 degrees Celsius when used by the same method. Replace the battery when the display dims. If the readings are consistently odd, replace the thermometer.

Ear and forehead. Keep the lens or sensor clean and dry; wipe gently with the soft cloth supplied. Use fresh probe covers. Check the ambient temperature range in the manual, since many fail outside it. Compare with a stick thermometer if in doubt.

Mercury glass thermometers. Replace them with digital ones and dispose of them safely. See digital thermometers: choosing and using them for older people.

Pulse oximeters

Accuracy check. Compare your oximeter with one at the clinic or hospital on a healthy person, or with your own finger and a family member's. Readings in healthy people at rest are usually in the mid to high 90s. A device that regularly reads much lower than the clinic's, or jumps widely, needs checking or replacement.

Maintenance. Clean the inside of the clip with an alcohol wipe, let it dry, and make sure the light windows are clear. Replace batteries when the display dims. A damaged spring, cracked lens or loose cover is a reason to replace.

Limits. Even a perfectly working oximeter is affected by cold fingers, nail polish and movement; see pulse oximeter accuracy. If the readings look strange, first fix technique, then suspect the device.

Weighing scales

Accuracy check. Put a known weight on the scale, such as a sealed 1 kg packet of sugar or rice, or a couple of them, or a set of weights from a shop, and compare. Better still, weigh on the clinic's scale and your own on the same day, in similar clothes.

Zero and stability. The scale should read zero when empty and give the same value on repeated weighing. Check it on a hard, flat floor. A wobbly scale or one that gives different numbers for the same person within a minute needs replacing.

Batteries. Weak batteries cause erratic readings or "Lo" messages. Replace them with fresh ones.

Feet and platform. Check rubber feet and the glass or plastic platform for cracks. See weighing scales and unplanned weight loss in older adults.

Air quality and other devices

Low-cost air quality monitors can drift with dust and age. Clean the inlet, compare with another device and expect a lifespan of a year or two for the sensor. See air quality monitors for homes with older adults.

Battery care in general

• Use fresh, matching batteries of the same brand and type; do not mix old and new.
• Prefer alkaline for devices used occasionally, and rechargeable if the maker says they are suitable.
• Remove batteries from devices stored for long periods.
• Keep spares in a labelled bag, away from heat.
• Dispose of used batteries at a collection point, not in household waste, where possible.
• Watch for leaks: white crust inside the battery compartment suggests damage; clean carefully with a dry cloth and replace batteries.
• Power cuts: choose battery-capable devices, and keep a spare set and, for rechargeable devices, a charged power bank.

Indian conditions

Heat, humidity, dust and monsoon damp shorten the life of electronics. Store devices in a cool, dry box away from the bathroom, the kitchen stove and sunny windows, with a silica gel packet. In summer, do not leave devices in a hot car, on a terrace or by a window. During the monsoon, check for condensation, mould in the cuff and rust on battery contacts. After a flood or major leak, replace devices that got wet. Pests such as cockroaches and ants can damage cables and cuffs, so keep the box closed. Voltage surges can damage adaptors; use the recommended adaptor.

When to replace

Replace a device when:

• Readings are consistently off compared with a trusted reference.
• It gives erratic or error readings after replacing batteries and checking technique.
• Physical damage: cracks, leaks, loose parts, a failing display.
• A part cannot be replaced and the device does not work well.
• Age: it has passed the maker's suggested lifespan.
• A recall or safety notice has been issued.
• You no longer trust it. Anxiety about a doubtful device is itself a reason to replace.

When buying a replacement, see health device budgets and quality checks in India, and dispose of old electronics through an authorised e-waste collector where available.

Keep records

Note the make, model, purchase date and warranty in your health record, along with the dates of checks and battery changes. Keep the receipt and warranty card in the device box. This helps if you need a claim, and tells the doctor which device produced the numbers.

When to ask a professional

Ask a doctor, nurse or pharmacist to compare your devices with theirs during a visit. Ask the maker or service centre about calibration checks. Seek advice if home readings differ from clinic readings or if numbers do not match your parent's symptoms. Do not make medicine decisions based on readings from a device you doubt. Call 112 for emergency symptoms, whatever the device shows.