ABB COMMANDER 1900 Series User Manual

Also see for COMMANDER 1900 Series: Programming guide Installation guide Programming guide Operating guide

Contents

ABB COMMANDER 1900 Series User Manual Manual pdf 20 page image

18…5 ADVANCED CONFIGURATION LEVEL5.1.2 Relative Humidity (RH)The relative humidity calculation requires two inputs, one from a wet-bulb sensor and one from a dry-bulb sensor. Both of theseinputs are configured as variables. RH tables are based on the use of an aspirated psychrometer having an air velocity of at least11.5 feet per second or 3.5 meters per second across the bulb sensors.Note. Inputs used for wet- and dry-bulb measurement must be in the ranges 32 to 212°F or 0 to 100°C .5.1.3 Mass Flow 1 and 2The two types of mass flow calculations available are as follows:Mass Flow 1 – applications where a volumetric flow meter is used to measure flow.Mass Flow 2 – applications where a differential pressure transmitter is used to measure flow.The standard formula for mass flow 1 is as follows:PTTrPrM = k Vwhere:k = Scaling constantV = Input a (input from volume flow source)P = Pressure (pressure input source)T = Temperature (temperature input source)T r = Reference temperature (for the scaling constant used)P r = Reference pressure (for the scaling constant used)The temperature units used by the input source must be specified, since all calculations use absolute temperatures andconversion is made if the input uses °F or °C.The standard formula for mass flow 2 is as follows:(i)h P TrT PrM = kwhere:h = differential pressure headSome differential pressure sensors incorporate a square root linearizer and therefore produce an output linear to flow. In theseinstances no additional linearization within the C1900 is required. Where the input from the differential pressure sensor is linearto differential pressure head the square root linearizer within the C1900, must be selected in the Linearizer Type frame in the SetUp Input Page, BASIC CONFIGURATION LEVEL.Therefore the formula used internally within the C1900 is:(ii)PTTrPrM = k awhere:a = linearized flow signalThe linearized flow signal is produced by the transmitter or derived from the signal linearized within the C1900.• Maths