Delta Controls DPT-2000 - Manual (Page 19)

17 IOM-DPT-A: FEB 2014
8.3. Protection from excess voltage
8.3.1 . The transmitters may be in danger from excess voltage caused by connection faults or atmospheric
electrical discharge.
Protection from excess voltage between the wires of the transmission line is provided by TVS diodes installed
in all types of transmitter (see the table, column 2).
8.3.2 . In order to protect against excess voltage between the transmission line and the casing or earth (not
prevented by the diodes connected between the transmission wires), additional protection is provided in the
form of plasma surge arresters (see the table, column 3).
Also external protective devices may be used, e.g. the UZ-2 Delta Controls system, or others. When the
transmission lines are long, it is advantageous to use one protective device near the transmitter (or inside it), and
another near entry points to other devices used in conjunction with it.
Internal protection of transmitters:
1 2 3
Type of
transmitter
Protection between wires (TVS
diodes) – permitted voltage
Protection between wires and earth and/or casing – type
of protection, permitted voltage
DPT...
(normal version)
68V DC Plasma surge arresters - 230V DC
DPT...
(Exd version)
68V DC Not applicable
DPT...
(Exi version)
39VDC Not applicable
8.3.3 . The voltage in the protective elements must not exceed the maximum permitted values given in columns
2 and 3 of the table.
The insulation test voltages (500V AC or 750V DC) given in 5.1.1 refer to transmitters plasma surge
arresters - such protection is not used in Exi versions of transmitters.
8.4. Earthing
The transmitters are fitted with internal and external earth terminals .
9. SETTING AND REGULATION
9.1. Measurement ranges, Definitions
9.1.1. Nominal range
The maximum range of temperature, which the transmitter can measure is called the “nominal range” (for
specifications of nominal ranges see section 5.3).
The width of the nominal range is the difference between the upper and lower limits of the nominal range.
The
internal characteristic conversion curve for the nominal range is coded in the transmitter’s memory .
This is the reference curve used when making any adjustments which affect the transmitter’s output signal.
9.1.2. Set range
When the transmitter is in use the term “set (calibrated) range” is used. The set range is the range whose
lower end-point corresponds to an output current of 4mA and whose upper end-point corresponds to a current
of 20mA (or 20mA and 4mA respectively when the conversion curve is inverted).
The set range may cover the whole of the nominal range or only a part of it.
The width of the set range is the difference between its upper and lower end-points. T
he transmitter may be set to any range within the nominal range of temperature values, subject to the
restrictions set out in the table in section 5.3
.
9.1.3. Factory range.
in case when lacks information about measuring range, transmitters are setting on " factory range".
/0 ... 100/ °C
– factory range for transmitter with Pt100 sensor.
/0 ... 300/ °C – factory range for transmitter with "K" thermoelement.
i