FormularyMIS

The process of measuring is experimentally obtaining one or more quantity values that can reasonably be attributed to that quantity, i.e. finding a value for something we want to measure that makes sense. The value to be measured is called the measurand and the values it gets are the results, along with relevant information like the unit.

The set of values we are measuring for some measurand can be represented by a bounded interval centered on the measured quantity value.
The error is bounded in that , where is called the uncertainty radius of this interval.

We call the absolute uncertainty of . If we can define the relative uncertainty as the ratio of the uncertainty to the magnitude of the measured value, how accurate this measurement was.

• Use at most two significant figures for uncertainty
• Use for the value a number of significant figures that makes sense for the uncertainty
• Make sure the value and uncertainty have the same unit
• Don't mix values and relative uncertainties, (this is commonly done but shouldn't be)
  Some examples of writing values and uncertainties the correct way include
  Passive components like resistors, capacitors and inductor scome in standard values and tolerances, e.g.

The uncertainty in an analog instrument is specified by the accuracy class index, defined Where:

• is the nominal full-scale range
• is the absolute uncertainty across all scales

Uncertainty in digital instruments is expressed in two forms, both of which involve the coefficients , or where it is expressed as

Where lsd stands for least significant digits also referred to as the resolution, referring to how many decimal points past the main value it can measure and so does the range, as in, the "smallest value" it can measure.

The law of propagation of uncertainty uses the Taylor Series Expansions of first order to determine how uncertainties for inputs affect the output , and then we properly define:

• Given the measurement function
  the general law of propagation of uncertainty is
  where the coefficients
  are called sensitivity coefficients

Voltmeters measure voltage. Voltmeters are connected in parallel. Reference polarity is defined by terminal labels and colors, where HI is red and is the positive terminal, and LO (COM) is black and is the negative terminal. Voltmeters are connected by test leads to the circuit.

A voltmeter draws current from the circuit it's measuring. We connect the voltmeter with an input resistance . For some load resistance connected to the voltmeter, we have
When connected to a circuit it will disturb the power balance of the circuit, and we define the loading error as
which can be neglected when
The input resistance for a voltmeter is specified by manufacturers in the instrument specifications. For a passive analog voltmeter the input resistance is usually proportional to the range, with , where is the specific input resistance. For a digital voltmeter the input resistance is typically or greater

Current is the flow of charge over time. It is measured by an ammeter, which is connected in series. The terminals it connects to are marked I, in red, representing the Input, and LO, in black, and are usually fused for protection. A real ammeter has a non-zero input voltage, called the burden voltage, and for the ammeter we have that

The ammeter burden voltage produces a loading error then, with
which can be neglected when
The ammeter input resistance is specified by manufacturers. Manufacturers also specfy the burden voltage at the nominal current range from which we have that

Materials offer resistance to current flow. This resistance is measured in Ohms, , with the Ohm's Law being defined
There are multiple methods for measuring resistance.

The ammeter-voltmeter method uses the definition of resistance by measuring either the current going through the resistive element or the voltage across it. The two methods are either ammeter-downstream or voltmeter-downstream, and we pick the one with the lowest error.

This configuration is appropriate for low to medium resistance values, when

This configuration is appropriate for medium to high resistance values, when