This document specifies the requirements for a hair string type hygrograph used to continuously and permanently record atmospheric humidity levels at a location. The hygrograph must comply with IS5900-1970 standards, have a measurement range of 0-100% relative humidity (RH) with an accuracy above 20% RH of 5% RH, a recording resolution of ±0.2% RH, and use a housing made of fiberglass reinforced plastic or aluminum containing a clockwork-driven drum mechanism to continuously record humidity levels on a chart.

1. 30.010 HYGROGRAPH, HAIR STRING TYPE
Approval Date: 20 May 1998 Version: 1
Equipment Specification: HYGROGRAPH, HAIR STRING TYPE Version 1 30.010-1/1
Purpose
To have continuous and permanent records of the atmospheric humidity at a place
Conditions & Requirements
• The general arrangement and main dimensions of the hair hygrograph and charts shall
comply with IS5900-1970.
Specifications
range 0 to 100% RH
accuracy above 20%: 5% RH
recording resolution ± 0.2% RH
housing material FRP or aluminium
recording mechanism drum, driven by clockwork