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hygrotest 650 HP: Special measurement transmitter for high humidity applications
High m moisture p processes a are e extremely d demanding High moisture conditions prevail in many industrial processes, i.e. therelative humidity is close to the 100% limit at which the air can no longer
hold the water and condensation is precipitated. A critical point in the
regulation chain is moisture measurement. High quality measurement
transmitters are today able to measure accurately even in the high
moisture range, however their reaction capability is severely reduced if the
probe works close to the dewpoint limit over hours and days.
Condensation protection:optimum protection inhigh humidity applicationsWood drying is one of the most demanding highhumidity applications. The hygrotest 650 HP providesthe optimum solution here. hygrotest 650 HP -20/120 testo
humidity sensor A, B: Both probes aresecurely attached by cable
(0.8 to 10 m long) to the
transmitter. Teflon cap
Probe lengthstandard: 210 mm
optional: 80...800 mm
Ø12 mm 2 analog outputs(0...20 mA, 4...20 mA,
0...1 V, 0...10 V), both 4-wire AB Additional Pt1000 Cl. A
for compensation
of “micro-climate”
Ø3 mm
length as
humidity probe
(cf. right) T[°C]
[g/kg] The i innovative T Testo s solution t to t the h high h humidity p problem 5 K B
Heating resistanceat the rear, constant
warming by 5 K A In the testo 650 HP, the testo humidity probe is heated at the rear, so that
a micro-climate is created around the probe (inside the sintered Teflon
filter), which is constantly 5 Kelvin warmer than the actual process
conditions. As the psychrometric chart shows, this causes the relative
humidity at the
moisture probe to sink from a range close to 100 %RH to
a lower value, e.g. of 73%. In this range, the Psychrometric chart reaction speed is on the onehand noticeably better than in the condensation range, and on the other
hand there is less risk of corrosionfor the probe .The actual process temperature is recorded by a separate, highly
accurate
temperature probe Pt1000 class A. On this basis, the micro-
processor built into the measurement transmitter computes the actual
humidity conditions in the process. In addition to 4 to 20 mA (4-wire), the
versions 0 to 20 mA and 0 to 1/0 to 10 V are available as analog outputs.
e.g. 73 %RH
Mist
“Micro-climate”probe conditions
after heatingProcess conditionshigh humidity100 %RH
x