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- Monitoring Temperature and Humidity
Monitoring Temperature and Humidity
| Industry | : Machinery, Environment |
| Product | : Paperless Recorder (DX) |
Overview
 |
 Applying the DX's mathematical functions, humidity is calculated using the dry bulb and wet bulb formulas based on input from a resistance temperature detector (Pt). The calculation follows the Perunta formula. |
Customer Needs
| - | To have the humidity calculation function be internal to the DX, since we want to monitor humidity along with the internal temperature of the environmental testing equipment |
| - | To use general purpose RTDs rather than specialized humidity sensors, and avoid depending on external instruments and complicated programming |
Process Outline
Signals are input from Pt type RTD sensors. Dry and wet
bulb temperature are measured with the Pt's, and the DX's
calculation function automatically calculates humidity based on
the measured values. The calculation is based on the Perunta
formula, and the multipliers in the formula are input ahead of
time as Kxx.
Dedicated humidity sensors or external computing units are not
needed to determine the humidity, resulting in reduced costs
and more compact instrumentation. The number of instruments
comprising the system is also reduced, resulting in higher
overall reliability.
Sensors can be hard to calibrate due to the difficulty of creating
a reference humidity. The DX overcomes this problem because
humidity is determined through a calculation, and calibration of
the input can be substituted with calibration of the Pt100ohm
range.
| <Example of Mathematical Function Settings on the DX> | ||
| Input: | Pt100 (or JPt100) | |
| CH1: dry bulb°C), CH2: wet bulb°C) | ||
| Computed result: Humidity displayed on CH37 (MATH channel) | ||
| Expressions and constants: Perunta formula | ||
| 31: 1+K9 | ||
| 32: 2+K9 | ||
| 33: EXP(K1/31+K2+K3*31+K4*31*31+K5*LOG(31)) | ||
| 34: EXP(K1/32+K2+K3*32+K4*32*32+K5*LOG(32)) | ||
| 35: 33*K10 | ||
| 36: 34*K10 | ||
| 37 : ((36-K6*K7*(K11+2/K8)*(1-2))/35)*K10 | ||
| K01 : -6096.9 | ||
| K02 : 16.636 | ||
| K03 : -0.027112 | ||
| K04 : 1.674E-5 | ||
| K05 : 5.6033 | ||
| K06 : 0.0012 (ramda) | ||
| K07 : 1.0133E+5 | ||
| K08 : 610 | ||
| K09 : 273.15 | ||
| K10 : 100 | ||
| K11 : 1 | ||
| K12 : 2 | ||
| K06 (ramda) value is set as follows | ||
| When wind speed is 0-0.5 m/s: 0.0012 | ||
| When wind speed is 1-1.5 m/s: 0.0008 | ||
| When wind speed is 2.5 m/s or higher: 0.000656 | ||
Yokogawa's Solution
DX
DX Series Paperless Recorders can
easily calculate humidity using RTDs
| - | Humidity calculated with a MATH function (optional) |
| - | Measured and calculated results saved electronically to local media while being displayed in real time on the large, color TFT display |
| - | Enables data sharing on the network (Ethernet compatible) |
Conclusion
DX series instruments allow you to determine temperature and
humidity and manage the results as manufacturing/quality data
at a reasonable cost with a simple configuration. No special
external equipment or humidity sensors are required, resulting in
overall cost reductions in the system.
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