An important performance parameter indicating transmitters is something often called "turndown" or "rangedown" or "rangueabilidad". The "Rangueabilidad" is defined as the ratio between the maximum span between the minimum span allowed for a single instrument in particular.

Suppose a pressure transmitter has a maximum calibration range from 0 to 300 PSI and a "turndown" of 20:1. This means that a performer can adjust the span to any value between 300 PSI and 15 PSI (300/20 = 15). It is very important to note that in order to select a suitable transmitter for any application. The odds of having a transmitter with factory calibration and never change its configuration is very small, which means that in any case will have to be adjusted to meet the needs of the specific application. The rangueabilidad tells us how or where we can set limits the range of our transmitters.

For example, suppose you are working in a facility where operations personnel requires that you install a pressure transmitter in a container with a measuring range of 50 PSI to 90 PSI. Then go to our shop or store where the new stock instruments, and found a pressure transmitter with a (maximum) range from 0 to 1000 PSI, and a turndown of 20:1 or rangueabilidad. Dividing the maximum span of 20 to 1000 PSI, we span the minimum allowed is 50 PSI, the span required for operating this transmitter is 40 PSI (90 PSI - 50 PSI) which means that the transmitter we have in store NOT be able to "reach" the desired minimum range. At best, we may set a range of 50 PSI to 100 PSI, or maybe 40 PSI to 90 PSI, but never at 90 PSI 50 PSI as required by operations. So far, we have to consult your operating span 50 PSI would be acceptable or not, or we will order a different pressure transmitter with a smaller span (or a higher value rangueabilidad).

Another important consideration with "turndown" or "rangueabilidad" is the "accuracy" of the instrument. Almost all instruments are set to their maximum span, and generally the worst accuracy occurs when the span is reduced. For example, the Micro Motion mass flowmeter "ELITE" means having a precision of + -0.05% at rangueabilidad to 20:1, and if accuracy is reduced to + -0.25% to rangueabilidad of 100:1, and a + rangueabilidad -1.25% to 500:1. We must realize the degradation of pressure on the measure rangueabilidad great values, here the mass flow meter is not to blame, but undoubtedly is a consequence of putting your rangueabilidad the limit.