Pneumatic Transmitters Model 175 Draft-Pressure Transmitters Introduction Description The Model 175 Draft-Pressure Transmitters are used primarily for general combustion or steam generating applications. The most common applications for these instruments are forced draft, induced draft, first- and last-pass draft, stack draft, fire-box pressure, and air- or fuel-gas flow. Each combines a slack diaphragm-type measuring element with a motion transmitter to create a sensitive and accurate instrument. Three basic models are available. They are: Model 175DL for differential-pressure ranges Model 175P for low-pressure ranges Model 175V (reverse-acting transmitters) for negativepressure applications Any range is available to produce a 3-15 psig output for spans as low as 0.16" H2O) to a maximum of 3.5 H2O. A threaded adjustment permits +25% variation of the nominal full-scale span. Another threaded (zero) adjustment accommodates +100% full-scale suppression. Range changes can be accomplished in the field by changing the range spring on the measuring element and by adjusting the motion transmitter. Specifications Static Damage Pressure Limit Supply Pressure ±5 psig Normal: 20 psig (1.38 bar) Maximum: 35 psig (2.41 bar) Minimum: 16 psig (1.10 bar) Air Supply Pressures Output Pressure Normal: 20 psi Minimum: 16 psi Maximum: 35 psi 3-15 psig (0.2-1.0 bar) Deadspot Response Level Within 0.2% F.S. 0.1% of span Hysteresis Reproducibility Within 2% F.S. 0.25% of span Non-Linearity Overrange Limit ±1% F.S. With normal 20 psi supply 16" H2O (3.99 kPa) 8 Ambient Temperature Limits Air Consumption 35 to 150°F (1.7 to 66°C) 0.1 scfm in balanced condition - dead end service Maximum Static Pressure (Model 175DL only) Supply Pressure Effect 5 psig (34.5 kPa) -0.04 psi change in output pressure for a 5 psi increase in supply for 0-1.0" H2O input span Normal Operating Limit On Static Pressure for Differential Pressure Units 16" H2O Receiver Gauge optional for local indication of process variable (may be threaded directly into tapped connection in a Model 75 transmitter. 8.13 Pneumatic Transmitters Model 175 Draft-Pressure Transmitters Technical data Range Change In some cases, the range of an instrument can be changed via calibration adjustments alone. In other cases, springs must be changed. Range Spring Selection Span In " H2O Pressure Element Spring Kit Motion Transmitter Spring (Nominal) .16 to .24 10801-4 Green 4950-5 Blue .25 to .32 10801-4 Green 4950-4 Green .33 to .45 10801-4 Green 4950-3 White .46 to .57 10801-4 Green 4950-2 Black .58 to .79 10801-3 White 4950-3 White .80 to 1.00 10801-3 White 4950-2 Black 1.10 to 2.10 10801-2 Black 4950-2 Black 2.20 to 3.50 10801-1 Red 4950-2 Black Mounting Dimensions 8 8.14