The 580 series dead-weight tester can be supplied in several different configurations. The series is based around the 580 series base unit which is common to all the different configurations. The base unit provides a pressure source, liquid reservoir, control valves and gauge or piston connections. When the base unit is used with one of the 580L, 580M, 580DX, 580HX or 580VHX piston units the configuration provides an high accuracy dead-weight tester.
580VHX PISTON UNIT
The 580VHX piston unit is a dual range piston unit covering the range up to 1400 bar (20000 Ib/in2 ) . The piston head which carries the calibration weights is operated by two pistons; a low pressure piston and a high pressure piston. As the supply pressure is increased the low pressure piston is operated until the flange on the end of the low pressure piston abuts the end of the low pressure cylinder. As the pressure continues to increase, the high pressure piston operates through the middle of the low pressure piston which is now acting as the high pressure cylinder. Indication of the range in which the piston is operating and that the piston head is floating is given by the position of the piston head as seen against two coloured bands on the cylinder. The pressure datum level of the piston unit is marked on the connection used to screw the piston cylinder unit on to the base unit pressure connection blocks threaded boss.
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