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in-hypalm-v40 / 20051205
Analog Probes (HygroPalm 3 only)
The HygroPalm 3 can be used with one or two analog probes. Both the scale and unit of the analog input
signals can be defined with the HW3 or HW4 software. For example, an analog pressure probe may used
to provide the local value of barometric pressure for the computation of parameters such as the wet bulb
temperature, mixing ratio or enthalpy.
Use of analog probes is subject to the following restrictions and limitations:
a. ROTRONIC analog humidity-temperature probes with the standard temperature output signal of –
0.5…2.0 V = -50…200 °C: because the HygroPalm cannot read a negative voltage signal, temperature
measurement is generally limited to values above freezing.
b. Third-party analog probes: single channel probes (one signal), output signal within the range of 0 to
2.5 VDC, supply voltage: 7.6…9 VDC (direct from HygroPalm battery), maximum current consumption:
10 mA.
c. Resolution is limited by the 10-bit A/D converter used for the analog inputs. This converter provides a
theoretical maximum of 1024 counts for an input voltage span of 2.5 VDC. In theory, this gives a
resolution of 2.5 / 1024 = 0.00244 V. In practice, it is not possible to get 100% of the counts from an
A/D converter and the actual resolution should be about 0.0027 V (typical). For example, if a probe
with a temperature signal of 0..1 V = 0…100°C is being used, the signal resolution will be about 100 x
1 x 0.0027 = 0.27°C
RS232 Serial Output
Both the HygroPalm 2 and HygroPalm 3 feature a serial (RS232) port that can be connected to the COM
port of a PC. In principle, any communication software can be used to read measurement data from the
HygroPalm with the commands described in appendix 6 (RS232 communication protocol). It is important
to note that the computed parameter (dew point or other) is not part of the digital communication.
Use of the HW3 or HW4 software (optional) allows real time computation of the dew point (or other) by
the PC while providing additional functionality such as:
- full access to instrument configuration (unit system, etc.)
- calibration of the ROTRONIC HygroClip digital probes independently of the HygroPalm (requires
the MOKX-03-WIN calibration cable to connect the probe to a PC)
- data logging to a PC disk file
- graphic functions (both on and off-line)
For more details see separate instruction manual provided with the HW3 or HW4 software.
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