HD2301
- 10 -
V1.7
PROBES AN D M EASUREM EN TS
The inst rum ent
H D 2 3 0 1 .0
works by using com bined hum idit y/ t em perat ure probes
( t em perat ure wit h a Pt 100 sensor) and wit h t em perat ure only probes wit h 4 w ir e
Pt 100, or 2 or 4 w ire Pt 1000.
The com bined hum idit y/ t em perat ure probes are fit t ed w it h
SI CRAM
m odule t hat act s
as an int erface bet w een t he sensor on t he probe and t he inst rum ent . There is a
m icroprocessor circuit wit h a perm anent m em ory inside t he m odule t hat enables t he
inst rum ent t o recognize t he t ype of probe connect ed and t o read it s calibrat ion
inform at ion.
The Delt a OHM Pt 1000 probes are aut om at ically det ect ed while t he direct 4 w ire Pt 100
t em perat ure probe is not aut om at ically det ect ed by t he inst rum ent and m ust be set
up in t he
Pr obe t y pe
m enu it em ( please see t he m enu descript ion on prev ious
chapt er) .
Th e pr obe is de t e ct e d du r in g t u r n on , a n d t h is ca nn ot be pe r for m e d w h e n t he
in st r u m e n t is a lr e a dy on , t h e r e for e if a pr obe is con ne ct e d a n d t h e
in st r u m e n t is on , it is n e ce ssa r y t o t ur n it off a n d on
.
M
EASUREM EN T OF RELATI VE H UM I D I TY
The hum idit y probes are " hum idit y and t em perat ure" com bined probes:
•
t he hum idit y sensor is a capacit at ive t ype sensor;
•
the tem perature sensor is a Pt 100.
The inst rum ent m easures relat ive hum idit y % RH and t em perat ure, and st art ing from
t he fixed barom et r ic pressure value of 1013.25 m bar it calculat es t he follow ing
result ing quant it ies:
1. g/ m
3
gram s of vapour in a cubic m et er of dry air
2. hPa Part ial vapour pressure ( hPa)
3. Td Dew point ( ° C or ° F)
P
ERFORM I N G TH E M EASUREM EN T
To perform t he m easurem ent , proceed as follows:
1. int roduce t he probe in t he area of whose param et ers you wish t o m easure.
Ca u t ion !
Keep t he probe far from elem ent s t hat m ight int erfer e wit h m easurem ent
such as: heat or sources of cooling, walls, air- st ream s, et c
Av oid t e m pe r a t u r e dr ops t h a t m igh t ca u se con de n sa t ion .
2. a reading t aken when no heat drop occurs is pract ically im m ediat e;
N OTE:
in condit ions involv ing
h e a t dr ops
, it is necessary t o wait unt il t he probes and
t heir housing have reached a t herm al equilibr ium in order t o pr event heat irradiat ion
or absorpt ion on t he relat ive hum idit y sensor which would cause a
fa u lt y
m e a sur e m e n t
.
3. since t em perat ure affect s relat ive hum idit y ; m ove t he probe lik e a fan in order t o
speed t he response t im e in t he presence of heat drops.
