Liquid Filled Thermometers

These instruments are used to detect the temperature in the oil filled transformers and are made for outdoor mounting in as well tropical or artic climates (ambient temperature range : -30 / +70°C). All components are made of corrosion resistant or surface treated materials.

Nominal diameter : 100mm or 150mm
Temp. sensing system : expansion type (liquid filled system), compensated for ambient temperature changing by means of a bimetallic spring.
Capillary protection :

• protective copper tubing
• flexible galvanized iron + PVC tubing
• flexible AISI 304 tubing.

Bulb : brass or stainless steel
Casing : aluminium alloy with powder painting high protection degree. On request case can be provided with an air breather device.
Locking clear window : glass.
Locking Ring : nickel plated, transparent coated.
Standard measuring ranges :

• -20 / +130°C
• 0 / +120°C
• 0 / +150°C
• 0 / +200°C

Measuring accuracy : 1,5% of full scale value.

These thermometers are equipped with electrical contacts of air type (silver contacts). On request the electrical contacts can be equipped with a little magneto to avoid uncertain commutations when the instruments are subject to vibrations. The contacts can be normally open or normally closed. The opening and closing of contacts are of slow action type.

Electrical Contacts Making and Breaking Capacity

Electrical Contacts Standard Execution

Volt	Alternating Current	Direct Current	Inductive Load
380	28mA	23mA	15mA
220	46mA	40mA	22mA
110	90mA	80mA	45mA
50	170mA	130mA	70mA

Magnetic Electrical Contacts

Volt	Alternating Current	Direct Current	Inductive Load
380	80mA	70mA	45mA
220	140mA	125mA	65mA
110	275mA	240mA	130mA
50	500mA	380mA	200mA

Insulation Test : 2000V 50Hz between terminals and earth for a 60 second time.
Mechanical Protection Degree : IP 55
Measuring Accuracy : 1,5% of full scale value.
Elastic Suspension : This device is a vibration damping system able to minimise the effects of machine vibrations on the instrument.

Operating instructions :

Mounting :
a) rigid stem thermometers ( types 1144/S – 1184/S – 1186/S ) fix the connection on the thermometer pocket by means of a spanner. Attention don’t try to tighten the con- nection by rotating the thermometer’s head as you may damage it ! Once the connection is fixed you may need to position the dial to get the best readability. The positioning can be made by means of the swivel nut of the thermometer.

b) thermometers with capillary (types 1187/S ) : fix the thermometer’s head to the machine by means of the back flange or of the elastic suspension. Then fix at regular distances the capillary to the machine wall or cover and position the bulb inside of the thermometer pocket. Finally tighten the connection.

Contact setting : remove the locking ring remove the glass rotate the frictioned setting pointers till are positioned at the desired set points value put the glass into its seat taking care that the sealing O-ring is correctly located under screw the locking ring.

Cable layout : Remove locking ring and glass as done for contacts setting connect the terminals of the contact by taking care that black screws correspond to black pointer contact and red screws correspond to red pointer contact Reposition the glass and mount the locking ring.

Maintenance : No particular maintenance is required. Only, on regular basis, schedule inspections to verify correct function and calibration. Typically a check of the precision must be done after 24 months and the check for contact functionality must be done at least once a year. In case the transparent is dirty, thus reducing the readability of the dial, you can clean it with a soft cloth, water and soap.

Thermometers without electric contact for distribution transformers

Instrument calibration : carried out through thermostatic baths controlled by a microprocessor based moni- toring unit. The procedure varies according to instruments scale. The calibration procedure, being the thermometer scale = 0 / +120°C is made by using 5 different baths set at the following temperatures :

• bath1= 0°C
• bath 2 = 20°C
• bath 3 = 50°C
• bath 4 = 100°C
• bath 5 =  115°C

Calibration procedure :

Step 1 : a check is carried out to see whether the temperature taken by the instrument under test differs from that taken through the sample sensor by more than the 70% of the maximum allowed instrument reading tolerance value. This test is performed by sequentially plunging the thermometer bulb into successive temperature increasing thermostatic baths : 0°C / +20°C / +50°C / +100°C / +115°C.

Step 2 : the instrument is heated until the instrument pointer exceeds by 20% the angular full scale value.

Step 3 : step 1 is repeated, but inversely.

Check of instrument mechanical protection degree : IP 55

Thermometer with electric contacts (air type silver contacts) for distribution transformers

Instrument calibration : carried out through thermostatic baths controlled by a computer system. The procedure varies according to instruments scale. The calibration procedure, being the thermometer scale = 0/+120°C is made by using 5 different baths set at the following temperatures :