TELEVAC MX2A, Instruction Manual

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Instruction Manual MX2A Active Thermocouple Gauge
(d) Linear 4
(e) Linear 3
(f) Linear 2
(g) Linear 1
B . RS-485 I/O
To make changes under the RS-485 I/O screen:
ˆ
Navigate to the RS-485 I/O screen.
ˆ
Press UP or DOWN to reach the desired RS-485 setting.
ˆ
Press ENT to unlock the setting.
ˆ
Press UP or DOWN to change the fields.
ˆ
Press ENT to save and lock the change.
The RS-485 settable fields are listed below. Please see the sections labeled RS-485 Commu-
nications and Changing Communications Parameters for more details and a complete list of
commands. Listed below are the fields within the RS-485 I/O screen.
(a) Address
(b) Baud Rate
(c) Stop Bits
(d) Parity
2.6 Analog Output
The MX2A provides the option for outputting the vacuum reading in an analog form. Operators who
wish to use PLCs to monitor processes should find this function useful. There are seven different
analog output formats to choose between. The formats include Logarithmic, Linear by Decade, Non-
linear, Linear 4, Linear 3, Linear 2, and Linear 1.
A . Logarithmic
The Logarithmic output is the most useful and accurate output for covering the entire range of
the 2A with an analog output. This format uses the formula below to convert the output voltage
into a pressure measurement:
Pr essr e
(
Tor r
) =
10
. 6 ×
(
Votge − 5
)
For example, a voltage reading of 3.075 Volts corresponds to pressure of .07 Torr.
10
.
6 ×
(
3
.
075 − 5
)
=
. 07 Tor r
B . Linear by Decade
The Linear by decade output spans the entire range of the MX2A. It uses the units digit of
the voltage reading to communicate the decade of the pressure reading and the units after
the decimal to communicate the specific pressure using the very generalized expression below,
where A, B, C, and D are digits ranging from 0-9:
Votge
=
A.BCD → Pr essr e
(
Tor r
) =
10
A − 6
× .BCD
For example, a voltage reading of 8.367 Volts corresponds to a pressure of 36.7 Torr.
10
8 − 6
× . 367
=
36 . 7 Tor r
C . Non-linear
The Non-linear option outputs the raw signal collected by the 2A sensor. The raw signal is
converted to the pressure using a many-point linearization process done by the MX2A. This
feature is used for diagnostic purposes.
email: sales@frederickscompany.com tel: +1 215 947 2500 web: frederickscompany.com mx2a_im rev F 12 of 17