Measuring instrument, an item of measuring equipment that makes it possible to read off the value of the measured quantity directly. In analogue measuring instruments the reading is taken from a scale, in digital ones it is taken from a digital display. In direct-conversion measuring instruments (a manometer or an ammeter, for example) the measured quantity undergoes one or several conversions and its value is found without comparison with a known quantity of the same kind. In comparison measuring instruments the measured quantity is compared directly with a quantity of the same kind reproduced by a material measure (examples are the equal-arm balance, the electrical measuring potentiometer and the comparator for material measures of length). The varieties of measuring instrument include integrating measuring instruments, in which the applied quantity is integrated over time or over another independent variable (electricity meters, flowmeters), and summing measuring instruments, which give the value of the sum of two or more quantities applied through different channels (a wattmeter summing the powers of several electrical generators). For the purposes of automating the control of technological processes, a measuring instrument is often additionally fitted with regulating, computing and control devices that act according to prescribed programmes.