voltage-reference
The Fluke 732A has among 10V and 1V references also a 1.018V reference (whereas the 10V is the "main" references and the others are formed by resistive voltage dividers).
While having multiple reference voltages is surely convenient, why exactly 1.018V? Some references have a \$2^N*10^M V\$ value, which makes somewhat sense for ADCs to better have steps of \$10^K V\$, but why exactly 1.018V here, what is the significance of this value?
A bandgap voltage reference is a circuit that is relatively easily made on an integrated circuit. The basic premise is that it uses two different sized NPN transistors driven at the same current, and the sum of these two voltages can be an accurate reference voltage near the bandgap voltage of silicon at 0K, which is 1.25eV. There are many descriptions of the circuit, which began as the Brokaw cell, then the Widlar bandgap, and then the many variations you can see today. The Wikipedia page is a decent brief read.
It has several benefits:
The traditional method for generating the reference voltage is to add the voltages at the two paths, which will give the typical bandgap voltage of 1.25V, or two forward diode drops. As supply voltages have dropped, there has been a push for lower output voltages. They typically use more current mirroring to derive an output voltage that is closer to a single diode drop.
While I have never seen the term "half-bandgap" while doing research on low-voltage reference circuits, there are plenty of bandgap reference based circuits with an output voltage of 0.5 - 0.7V.
All voltage references have a tolerance and a drift with aging and temperature. This list includes zener diodes, series voltage references (like voltage regulators) and shunt references (like the normal zener). Here's what a BZX84C zener looks like: -
Take the 5V1 device - its zener voltage range is somewhere between 4.8V and 5.4V for a zener current of 5mA - if you put more current through it some devices exceed the 5.4V limit - notice the column marked "dynamic resistance - this also indicates how this "perfect" voltage might vary with an increase in zener current. Devices like the 7.5v are much better at regulating but their potential drift is slightly higher (see temperature coefficient column). For this particular type of zener I would want, for a better quality of regulation to be choosing the 7.5V device. Notice also that at low zener values the leakage current and dynamic resistance and temperature coefficient are not very good.
The temperature coefficient column is not "parts per million" but hundreds of parts per million per ºC. Compare the lowly zener with (say) an ADR5041. It has an initial accuracy of 0.1% and a TC of 75ppm / ºC and there are better devices than this....
The LTC6655BHLS8-2.5 - it has a temperature drift of less than 2ppm / ºC. Hey, it costs a lot more but if you want a precise, reliable voltage reference for your 16 ADC then go for it. If you want accurate and reliable measurements you need a stable and precise reference. If you are just wanting to stop your MOSFETs gate being damaged by over-voltage then look no further than a zener diode.
Best Answer
That is approximately the voltage produced by a Weston cell, a highly stable electrochemical cell historically used for calibrating voltages. The voltage has been retained so that comparisons can remain accurate even though the cell itself is no longer popularly used.