To Next Page

To Previous Page

%3*45&&.7BQPSMPHJD*OTUBMMBUJPOBOE0QFSBUJPO.BOVBMt1BHF

Calculation of transmitter % RH

% RH =

(mA reading) – 4 mA

16 mA

Example:

12 mA – 4 mA

0.16 mA

Modulating demand signal control

With modulating demand signal control, a modulating humidistat

or a building automation system sends a signal to the Vapor-logic4

controller, which then sends a signal to the humidifier to produce

a directly proportional steam output. For example, if a humidistat

operating between 4 mA and 20 mA sends a 4 mA signal, the

humidifier produces no output; a 12 mA signal causes the

humidifier to run at 50% of capacity; and a 20 mA signal causes

the humidifier to run at 100% capacity.

With a humidistat provided by DRI-STEEM producing this

signal, the humidity set point is set at the humidistat. The

keypad/display then is used for maintaining and troubleshooting

the humidification system, with humidifier control stemming from

the humidistat itself. With a building automation system (BAS)

providing the signal, the humidity set point is established by the

BAS, and the humidifier responds to the BAS commands.

Transmitter control

With transmitter control, the Vapor-logic4 board receives a signal

that corresponds to the actual humidity level measured in the space

being controlled. (With a transmitter provided by DRI-STEEM,

the signal is 4 to 20 mA, which corresponds to 0 to 100% RH). The

Vapor-logic4 controller employs an internal PID loop that uses this

humidity measurement along with a user-defined humidity set

point to calculate a demand level. This demand level is the level at

which the humidifier will run. See “PID tuning” on Page 51.

4UFQo'JFMEXJSJOH

$POUSPMJOQVUTJHOBMT

Installation

x 100%

= 50% RH

DriSteem Vapor-logic 4 User Manual

Questions and Answers: