MTL Instruments TP-AC Specifications

Technical data

MTL surge protection

MTL TP-AC range

October 2015
EPS 901-177 rev E

Safeguards electronic process
transmitters against induced
surges and transients from field
cabling

• Corrosion resistant

• Protects AC power and signal line

• 120V & 240V

• Models for Foundation fieldbus™ 4-20mA

and Profibus DP

• Parallel connection avoids resistance in

loop

• Easy and direct mounting – screws into

spare conduit entry

• 10 year product warranty

The TP-AC range of surge protection devices uniquely provides a level

of protection for AC powered, field -mounted transmitters that is far in
excess of the optional transient protection facilities available from the
transmitter manufacturers - and achieved without any additional wiring
modifications or costly additions.

The TP protection network consists of high power, solid state
electronics and a gas-filled discharge tube (GDT) capable of diverting
20kA impulses. The whole unit is encased in ANSI 316 stainless steel
housing, threaded for attachment in conduit entries used on process
transmitters. Versions are available with ½” NPT threaded entries.

Installation can easily be carried out retrospectively to existing
installations. The TP-AC is screwed into any unused conduit entry on
the transmitter case and flying leads are connected to the terminal
block signal, power and earth terminals. The TPs operate – passing AC
and DC signals without attenuation – while diverting surge currents
safely to earth and clamping output voltages to specific levels.

The all-important earthing connection is made to the local casing
of the transmitter with no separate earth connection or ground stake
at the transmitter being needed. In operation, the TP makes sure that
the transmitter electronics are never exposed to damaging transients
between lines or between lines and casing/earth. Any surge current
appearing as a series-mode or common-mode transient is converted
into a common-mode voltage, whereupon the transmitter electronics
are temporarily raised to some higher voltage level before “floating”
down automatically (and without damage) to resume normal operation.

For Fieldbus applications, the TP-AC Fieldbus models meet the
requirement of IEC61158-2:2004 and ANSI/ ISA-50.02-2 1992 for

31.25kbit systems as used by Foundation Fieldbus™, Profibus PA and
WorldFIP.

Measurement Technology Limited,
Great Marlings, Butterfield, Luton
Beds, LU2 8DL, UK.
Tel: + 44 (0)1582 723633 Fax: + 44 (0)1582 422283
E-mail: [e-mail]
www.mtl-inst.com

© 2015 MTL
All Rights Reserved
Publication No. EPS 901-177 rev E 131015
October 2015

1

MTL TP-AC range

October 2015

SPECIFICATION

Maximum surge current

20kA peak current (8/ 20μs waveform

Leakage current

Less than 10μ A at max. working voltage

Resistance
No resistance introduced into loop
Ambient temperature limits

-40°C to +85°C
(- 40°F to +185°F) (working)

-40°C to +85°C

-(40°F to +18 5°F) (storage)

Humidity
5% to 95% RH (non-condensing)
Casing

ANSI 316 stainless steel hexagonal bar stock, male
thread

Ingress Protection

IP6 6 (NEMA4X )

Threads

1/2” NPT

EMC compliance

To Generic Immunity Standards EN61326 -1, part 2 for
industrial environments

Dimensions

See figure 1

Weight

204g (7.2oz)

Model TP-AC

24 0VAC 120VAC

Pair (All models)

TP-ACFF

Foundation

Fieldbus Pair

TP-AC420

4-20mA

Pair

TP-AC485

Profibus DP

RS485

Pair

Nominal Voltage

Rated Voltage (MCOV)

Nominal Current

Nominal Discharge Current (8/20µs)

Max. Discharge Current (8/20µs)

Residual Voltage @ i

sn

Voltage Protection Level @ 1kV/µs

Bandwidth

Capacitance

Series Resistance

U

U

i

I

max

U

U

f

I

sn

n

c

n

p

p

G

C

R

240VAC 32VDC 48VDC 7VDC

275VAC 36VDC 58VDC 9VDC

N/A N/A N/A N/A

3kA 3kA 3kA 3kA

20kA 20kA 20kA 20kA

800V 65V 95V 19V

500V <50V <76V <12V

400Hz 7.5MHz 1M Hz 1M Hz

N/A 50pF 100 pF 100pF

N/A N/A N/A N/A

Operation Temperature Range -40º C to +85ºC -40º C to +85ºC -40º C to +85ºC -40º C to +85ºC

TP-ACFF-N AC power & Foundation Fieldbus 1/2” NPT Thread

TO ORDER SPECIFY:

TP-AC420 -N AC power & 4-20mA 1/2” NPT Thread

TP-AC4 85 -N AC power & Profibus DP (RS485) 1/2” NPT Thread

Figure 1: Dimensions

18.0 [457] typ.

Measurement Technology Limited,
Great Marlings, Butterfield, Luton
Beds, LU2 8DL, UK.
Tel: + 44 (0)1582 723633 Fax: + 44 (0)1582 422283
E-mail: [e-mail]
www.mtl-inst.com

© 2015 MTL
All Rights Reserved
Publication No. EPS 901-177 rev E 131015
October 2015

2

EUROPE (EMEA):

[phone]
[e-mail]

THE AMERICAS:

[phone]
[e-mail]

ASIA-PACIFIC:

[phone]
[e-mail]

The given d ata is only intended as a p roduct
descrip tion and sho uld not be reg arded as a leg al
warrant y of properties or gu arantee. In th e interest
of further technical developments, we reserve the
right to make de sign changes.