Dinel ULM-55N, ULM-55 Series, ULM-55Xi Instructions Manual

Ultrasonic level meter ULM-55 - instructions

I. Description

The ULM-55 ultrasonic level meter is designed for continuous non-contact measurement of the level of liquids
and mushy and paste-like substances in open and closed vessels, reservoirs, sumps etc. Depending on the working
area, the N type can be applied in environments not exposed to the danger of explosion, whereas the Xi type is
intended for use in explosive environments.
Table 1 contains classifi cation of the environments.
The adjusting elements of the level meter are situated on the rear side of the sensor, under the cap nut (see
chapter V).

Table 1: Meter type and description of working areas (according to the Norms EN 60079-14, EN 60079-10)
ULM-55N non-explosive area

ULM-55Xi II 1/2G Ex ia IIBT5 with isolating repeater (e.g. IRU-420) complete level meter zone 1
front part of head zone 0

The level meter ULM-55 transmits by electro-acoustic transducer the series of ultrasonic pulses, which propa­gate towards to the level. Refl ected acoustic waves are received back by the transducer and processed in the
electronic module. The echos are traced in the fl oating time window, the time of the wawes fl ight are fi ltered and
averaged. Further is made the thermal compensation and the signalis transferred to the output current 4÷20 mA. If
continuing echo fault happens, the current of the level meter slowly falls down to the value <3,8 mA. When the level
is moving in the dead zone (see the catalogue’s data) the output current rises up to the alarm value >21 mA. This
value is kept, untill the level meter doesn´t register the continuous motion of the level away from the dead zone to
the nominal measuring range (jumping distance is evaluated as a permanent fault).

II. Assembly and disassembly

Level meters are installed in vertical position into the upper lid of a reservoir or a vessel, using welded-on piece,
nut or fl ange. The axis of the level meter must be perpendicular to the surface of the liquid being measured. The
installation point must be chosen in such way so that the emitted acoustic signal is not affected by near objects (re­inforcements, ladders, mixing devices etc), liquid being poured inside, air fl ow etc. If in doubt, we advise to consult
it with the producer. The level meter housing need not to be grounded. Recommended dimensional parameters for
the level meter installation are shown in fi gure 1.

III. Installation

Terminals for electric connection are inside the dismountable GDM connector. Connect the positive pole (+)

ULM-55N-10

b > 100 mm
a / b < 1,5
c > 2000 mm
c / d < 8

ULM-55_-06

b > 100 mm
a / b < 3
c > 800 mm
c / d < 8

ULM-55_-02

b > 100 mm
a / b < 3
c > 500 mm
c / d < 8

Figure 1: Recommended dimensional parameters - dimension "a" must be as minimal as possible

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to terminal 1 and the negative pole (0 V) to terminal 2 – see fi gure 2 and 3. While making the connections the cable
must not be energised!
The level meter is connected to an evaluating device using a suitable two-core cable with an external diameter of
6-8 mm (recommended cross section of cores: 0,5 – 0,75 mm2). A shielded cable must only be used if the lead is
longer than 30 m or in the case of parallel lead togheter with power lines.
For supplying we advice a stabilized supply unit of safe voltage 12-30 VDC (SELV type), which can be part of the
connected evaluating device (for the ULM-55N type) or through an intrinsically-safe isolating repeater with supply
voltage 12-30 VDC, e.g. IRU-420 (for the ULM-55Xi type).

+U

shielding

0V

Figure 2: The inside of the GDM connector

Figure 3: Connection scheme

IV. Putting the unit into operation

The ULM-55N type: switch on the power supply (12-30 VDC).

The ULM-55Xi type: switch on the intrinsically safe isoating repeater (IRU-420).

V. Setting up

The level meter is set up by following steps. Use the adjusting elements located under the cap nut to set the
unit up – see fi gure 4.

Procedure:

1. Level meter is connected to the supply line via a miliampere meter (controller, etc.).

2. Disconnect the connector for access to adjusting elements and unscrew the cap nut (mind the internal wires).
Connect again the connector.

3. Empty the tank to the minimum level or put the level meter to the corresponding distance. Set the static current
by "4 mA" trimer to 4 mA.*

Turning to the right (clockwise) increases the current, while turning to the left decreases the current.

4. Fulfi ll the tank to the maximum level or put the level meter to the corresponding distance. Set the static current
by "20 mA" trimer to 20 mA.*

When it is impossible to fulfi ll the maximum level, then can be used any known (detectable) level and then set

appropriate current by next calculation:

I out = 4 + (0,16 x the level height in %) [mA]

5. To achieve maximum accuracy, it is advisable to re-check the setting of both limit values.

*

The trimmers do not have stop pieces – they can be turned approximately 15 times.

green-yellow wire

(shielding)

blue wire

(-)

trimer 4 mA

(minimum level

setting)

Figure 4: Adjusting elements

(top view of the internal electronic part)

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brown wire

(+)

trimmer 20 mA

(maximum level
setting)