All generally used pressure scales are standard in each instrument, practically eliminating the need to purchase extra meters as measurement requirements change. Each model has a carefully selected measurement range and can measure positive and negative (vacuum) gauge or differential pressures.Measurements, including maximum and minimum readings, can be held and displayed in any available scale. The adjustable zero value, to compensate for ambient temperature fluctuations, is also permanently held in memory, until changed by the user. The selectable, averaged reading function provides a further aid to accuracy by filtering out transient readings to give a more stable displayed reading. Each instrument can display its maximum pressure and has over-range indication.