Pressure gauges

Front View Shroud removed, revealing innards

(I always take things to bits.

They are for general commercial use in such applications as portable equipment, air lines and machinery, these gauges use the well-proven Bourdon tube as the active sensing element. They are intended for non-corrosive liquids and gases, having brass/bronze internal parts.

They were ordered from Thermospeed, stock no 329-302, rated at 0-1 bar/0-15 p.s.i.,  priced at 5.95 each.

Case style Black, injection moulded
Lens Clip-in polycarbonate
Internal parts Brass/bronze Bourdon tube, soldered; brass movement
Process connection 1/4" BSP brass, Centre-back connection all stem mounting
Pointer Black anodised aluminium
Dial Aluminium, white with black numerals dual scale bar/psi
Accuracy 1.6% FSD
Operating temp. -25...+60C
Working pressure Steady pressure 70% of FSD, fluctuating pressure 65% of FSD

I performed an accuracy test. (OK, I was fiddling - I just wanted to prove I knew what's going on.) Taping them to gravity fed water taps in the house supply I read .34 bar on the first floor, and .55 on the ground floor. The physical distance between the taps and header tank was measured. The distances were converted to the equivalent bar pressure. This site http://www.eonline.co.uk/eonlineweb/frameset2.htm has a useful conversion table. (Use Pressure Converter) .1 bar is equivalent to a head of 401.51" of water. I obtained an error of 6 inches from top of the water of header tank to kitchen sink hot tap. 2.5%  - not bad!

Two of these devices have been fitted to my upgraded central heating system: 

The gas boiler gauge (0..1 bar) reads 0.3 bar or 0.6 bar when the pump runs.

The solar gauge (0..4 bar) reads 1 bar, 1.2 when the pumps runs.