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Reference Manual
IP2048/RM, Rev AA
Appendix F: Configuring Using HART
February 2015
Mobrey MCU900 Series control unit
To view or change the lost echo action:
1. From the Main Menu screen, select SETUP.
2. Select the transmitter (e.g. “Tx1:MSP400RH”).
3. Select ENGINEERING.
4. Select LE Action.
5. Follow the on-screen instructions to edit and save the new setting.
(Press the Enter ( ) key if prompted to change mode to “off-line”).
6. Select “Quit” to exit to the previous menu.
F.3.26 Speed of sound (P024)
This is for entering the speed of sound of the gas above the liquid surface (ullage gas) in a closed
tank at 32 F (0 C) (see Ta ble F -2).
A new speed of sound is then calculated for the ullage gas at the temperature and humidity level
in the tank (see calculated Speed of Sound on page 158). The correction for temperature
effects is made using the parameter Temperature (page 132) and assumes the entered Speed
of Sound (P024) value is valid at 32 F (0 C).
For systems monitoring aqueous liquids with air (or nitrogen) as the primary gas in the ullage
space, the entered Speed of Sound (P024) value should be 1088.6 ft/s (331.80 m/s). This is the
most accurate setting for temperatures in the range of 32 to 104 F (0 to 40 C).
If the tank vapor space is filled with a different gas, a revised Speed of Sound (P024) value should
be entered. Gas mixtures have speed of sound values calculated as an average according to the
proportion of the gases present.
Table F-2. Speed of sound for ullage gases at 32 F (0 C)
Fast Keys
2, 2, 5 [or 6], 4
Ullage Gas
Speed of Sound
ft/s (m/s)
Ullage Gas
Speed of Sound
ft/s (m/s)
Acetaldehyde 800.53 (244) Ethylether 675.85 (206)
Ammonia 1361.55 (415) Methane 1410.76 (430)
Argon 1010.50 (308) Methanol 1099.08 (335)
Benzene 580.71 (177) Nitrogen 1105.64 (337)
Carbon Tetrachloride 475.72 (145) Nitric oxide 1095.80 (334)
Cyclohexane 593.83 (181) Oxygen 1089.24 (332)
Ethane 1036.35 (316) Propane 780.84 (238)
Ethylalcohol 846.46 (258) Sulphur hexafluoride 436.35 (133)
LE Action P022
Hold
Esc=Quit =Edit
(Mobrey MCU901 Screen)