NZGS 2 — datasheet

The specifications of the NANOZ NZGS 2 on one page, taken from the datasheet in revision 3.3.0 dated 29 September 2023. If you are designing it into a circuit you will find voltages, resistances, pinout and package dimensions here; if you are still checking whether it fits, you will find the warranted limits of detection and the operating limits.

What NZGS 2 is

An analog component: four metal-oxide sensing elements and two heating elements, manufactured in MEMS technology on a silicon substrate and housed in a QFN-8 package. The die measures 1.15 × 1.15 mm, the package 2.8 × 2.8 mm at a maximum height of 1.6 mm. A hydrophobic filter with 0.1 µm efficiency protects the sensitive layer inside the package.

What is measured is the change in sensor current or resistance in the presence of gas. Because each heater and each sensor can be biased independently, the component delivers several mutually independent signals for the same gas event — the basis of the selectivity explained in detail on the technology page.

Warranted limits of detection

The datasheet states limits of detection for these five gases. They were determined after 24 hours of stabilisation at 25 °C and 45 % relative humidity.

Hydrogen, ammonia, methane, hydrogen sulphide, nitrogen dioxide, ozone, nitrous oxide, BTEX and the electrolyte vapours EMC, DMC and DEC are also detected. The datasheet contains no warranted values for these; measured data and test conditions are provided per project.

Electrical specifications

In operation the heater voltage is not held constant but swept triangularly between the limit values. That modulation is what produces the four different response patterns from which classification determines the gas.

Pinout

Eight pins in the QFN package, 0.65 mm pitch:

Package dimensions

All figures in millimetres. BSC denotes a basic dimension without tolerance, REF a reference value.

Processing and handling

• Supply form: tape and reel, suitable for automated placement.
• Soldering: reflow according to the profile given in the datasheet.
• ESD: NZGS 2 is an ESD-sensitive component. NANOZ recommends the use of ESD protective equipment when handling.
• Silicone: silicone compounds poison the sensitive layer permanently. Sealants, adhesives, lubricants and release agents used in production must be silicone-free.

Operating and storage conditions

Operation: −10 to +85 °C at 15 to 90 % relative humidity.
Storage: −40 to +125 °C at 10 to 95 % relative humidity, non-condensing.

First use: before first use the component must be pre-heated for 24 hours — at 2.3 V on the heaters and 0.8 V on the sensors, a higher heater voltage than in later operation. Baseline recording in clean reference air follows.

The datasheet also contains calibration curves for gas sensitivity and for the dependence on temperature and humidity, each referenced to 25 °C and 45 % RH.

What the read-out electronics must provide

NZGS 2 does not deliver a bus signal. What the component gives you are four sensor currents, or resistances, and those have to be captured while the heater voltage sweeps. Three points determine the circuit design:

• Heater driver. Two heaters of 111 and 118 Ω at 1.8 to 2.2 V draw around 70 mW together. The voltage has to be swept in a triangular waveform — a PWM output with a low-pass filter is sufficient, provided amplitude and period stay stable.
• Signal acquisition. Four channels with sensor resistances between roughly 155 and 550 kΩ. The front end has to stay linear across that range, and sampling has to cover the whole period, not just the peak value.
• Accompanying quantities. Temperature and humidity belong in the measurement, because both shift the signal and compensation otherwise has no data basis.

Classification itself then runs in the microcontroller. The model is tailored to the use case; the component underneath stays the same.

How an evaluation runs

Before integration comes the question of whether the target gases separate cleanly in your own environment. That cannot be derived from specifications, only measured. The evaluation kit with read-out electronics and software exists for exactly that: it records the four signal traces, extracts the features and shows whether the target gases fall apart in feature space.

What gets recorded is reference air for the baseline, the target gases at known concentrations, and the interferents that realistically occur at the installation point — the last of which decides the later false-alarm rate. Added to that are the boundary conditions temperature and humidity across the expected range, plus several sensor specimens, because characteristics vary.

Delivery form and samples

NZGS 2 is supplied on tape and reel and is thus prepared for automatic placement. For sample orders, quantities and lead times, please write to us briefly describing the application behind it — that determines whether a bare component sample is enough or the evaluation kit is the more sensible entry point.

What the datasheet does not warrant

NANOZ states explicitly in the datasheet that the figures given are typical characteristics. They vary from chip to chip and depend heavily on the specific application. Only the properties described in the datasheet are warranted.

In practice that means an alarm threshold or a measurement accuracy cannot be derived from these numbers, only from a measurement in your own gas matrix. Before use in an application NANOZ recommends consulting its technical team.

Further reading: how selectivity arises · applications · FAQ