Browse Calibration Instruments
What we calibrate
Our accredited laboratory covers five measurement areas. Our IANZ Scope of Accreditation lists the exact ranges and uncertainties we’re accredited for.
Pressure calibration
Pressure calibration compares your instrument with a reference standard of known accuracy at several points across its range. Readings are usually taken as the pressure rises and again as it falls, so the calibration shows both accuracy and hysteresis. Pressure instruments are especially prone to drift from vibration and pulsation, so regular calibration matters on pumps, compressors and hydraulic systems.
Temperature calibration
Temperature sensors are calibrated by comparison: the sensor and a reference thermometer are held at the same stable temperature in a stirred liquid bath or dry-block calibrator, and their readings are compared at each test point. Between full calibrations, an ice point check (a reading at 0 °C) is a simple way to confirm a reference thermometer hasn’t shifted.
Infrared thermometer calibration
Infrared thermometers measure the heat radiated from a surface, so they’re calibrated by aiming them at a blackbody source, a target held at a known temperature with a known emissivity. The instrument’s emissivity setting and its distance from the target both affect the result, so the calibration certificate records the conditions used.
Humidity calibration
Humidity instruments are calibrated by placing them in a controlled environment at set humidity levels and comparing their readings with a reference hygrometer. Humidity sensors are sensitive to contamination and ageing, which is why they need regular calibration.
Gas detector calibration
Gas detectors are calibrated by exposing the sensor to certified calibration gas of a known concentration. The detector is zeroed in clean air, adjusted to read the known gas concentration correctly, and its alarm points are checked. Teltherm operates the only IANZ-endorsed gas detection laboratory in New Zealand. In certain circumstances we can also calibrate gas detection equipment on site, and we’re the only company in New Zealand that can provide an IANZ-endorsed certificate for that on-site work.
In our laboratory or on your site
Our calibration laboratory was established in 1994, and we keep investing in its equipment, facilities and capabilities. You can choose where the work is done.
Laboratory calibration
We recommend laboratory calibration wherever possible. Our reference equipment is on hand, and so are the component parts needed if an instrument needs adjustment or repair. A dedicated customer service team looks after your instruments from booking through to return.
On-site calibration
Some instruments are too large or fragile to send away, or can’t be taken out of a critical process for a few days. Our field calibration team comes to you instead, working around your schedule. On-site calibration is available throughout the wider Auckland area, and elsewhere in New Zealand by prior arrangement. The team calibrates your equipment, makes adjustments or repairs where needed, and documents the results on our calibration certificates.
Repair, service and replacement
What sets us apart is that calibration doesn’t have to be the end of the conversation. If an instrument fails, we can repair, service or replace many types of instruments, so you get back to work sooner with less process downtime. See Service, Repair & On-site Calibration for more.
Traceability and accreditation
A calibration is only as good as the chain of measurements behind it. Traceability and accreditation are the two things that make a calibration certificate worth relying on.
What traceability means
Metrological traceability means a measurement result can be related to a national or international standard through a documented, unbroken chain of calibrations. Each link in that chain adds to the measurement uncertainty. Traceability gives you three things:
- confidence that your measurements relate to a known, accepted standard
- a stated measurement uncertainty for your results
- measurements that are accepted between countries.
The traceability chain
At the top of the chain is the International System of Units (SI), maintained through the International Bureau of Weights and Measures (BIPM). The BIPM was established under the Metre Convention and organises international comparisons, so that measurements made in one member country are accepted in others. Below it sit the national metrology institutes; in New Zealand, that’s the Measurement Standards Laboratory (MSL). Accredited laboratories such as ours calibrate their reference standards against the national standards, and then calibrate your working instruments.
ISO/IEC 17025 and IANZ accreditation
ISO/IEC 17025 is the international standard for testing and calibration laboratories. Accreditation to it shows that a laboratory runs an effective quality management system and is technically competent to produce valid results. Our pressure, temperature, gas and humidity laboratories are accredited by International Accreditation New Zealand (IANZ), which independently assesses us against the standard.
International recognition
IANZ is a signatory to the International Laboratory Accreditation Cooperation (ILAC) Mutual Recognition Arrangement. As a result, calibration results from IANZ-accredited laboratories are accepted by accreditation bodies, regulators and customers in the many countries that belong to the arrangement.
Our calibration capabilities
Our calibration and measurement capabilities (CMC), the ranges and best uncertainties we’re accredited for, are published in our IANZ Scope of Accreditation. Our team can help you work out which calibration you need and explain the results on your certificate.
How often to calibrate
Your instrument documentation or quality system should set the calibration interval. If it doesn’t, use the guide below as a starting point. If you’ve lost confidence in an instrument’s readings, get it calibrated, whatever the schedule says.
Recommended calibration intervals
| Instrument | Full calibration | In between |
|---|---|---|
| Pressure instruments | Every 12 months | – |
| Reference temperature instruments | Every 5 years | Ice point check every 6–12 months |
| Working temperature instruments | Every 12 months | Ice point check every 3–6 months |
| Humidity instruments | Every 12 months | – |
| Infrared thermometers | Every 12 months | – |
| Gas detectors | Every 6 months | Bump test before each use |
A bump test exposes a gas detector to a small amount of test gas to confirm it responds and alarms. It checks the detector is working, but it doesn’t replace calibration.
Our calibration reminder system lets you know when each instrument is next due, so nothing slips through.
Frequently asked questions
How often should my instruments be calibrated?
Follow the interval in your instrument documentation or quality system. As a general guide, most pressure, temperature, humidity and infrared instruments are calibrated every 12 months, and gas detectors every 6 months. Calibrate sooner if you have any doubt about an instrument’s readings.
What’s the difference between traceable and accredited calibration?
Traceable means the result links back to a national standard through an unbroken chain of calibrations. Accredited means an independent body, IANZ in New Zealand, has assessed the laboratory’s competence to ISO/IEC 17025. An accredited calibration is traceable, and the way the laboratory works out its uncertainty has been independently checked.
Can you calibrate my instruments on site?
Yes. Our field team calibrates on site throughout the wider Auckland area, and elsewhere in New Zealand by prior arrangement. We still recommend laboratory calibration where possible, because our full reference equipment and spare parts are on hand.
What happens if my instrument fails calibration?
We’ll let you know and talk through the options. We can adjust, repair or service many types of instruments, or help you replace one that can’t be brought back into specification.
What is a gas detector bump test?
A bump test is a quick functional check. A small amount of test gas is applied to confirm the detector responds and alarms. It should be done before each use, but it doesn’t replace six-monthly calibration.