United Kingdom
Pickering Relay
United Kingdom

LOW THERMAL EMF

Pickering’s Series 100 and 101 have internal thermal EMF levels as low as 1 microvolt for single pole types or even lower for two pole types used for differential switching, where there can be some cancellation of the thermal EMF voltages from the two switches.

Reed Relays for Direct Drive from CMOS - Series 100

In very low-level applications or where high accuracy measurements are important, the presence of thermal EMFs can cause unacceptable errors. For example, when switching thermocouples where temperature monitoring is required, or data acquisition where the signal levels from transducers are very low, a voltage introduced by a thermal EMF can create significant accuracy issues.

The design of the Pickering Series 100 and Series 101 reed relays helps to minimize the heating effect of the coil, the prime reason for the temperature gradients across the reed switch that creates the thermal EMF voltages. With values as low as 1 microvolt generated across the closed switch, this is significantly lower than an industry standard reed relay or an electromechanical relay. Using a 2 Form A relay with the switches connected differentially, there can be some cancellation of the thermal EMF voltages generated from the two switches resulting in even lower values, making these reed relays an ideal solution when switching thermocouples.

The Series 100 and Series 101 offer 1 Form A, 2 Form A, 1 Form B and 1 Form C configurations, all featuring magnetic screening to allow for side by side stacking and instrumentation grade reed switches to ensure long life. The low coil power consumption also makes these reed relays ideal for portable equipment.

Recommended Reed Relays for Low Thermal EMF

Series 100 – Low Thermal EMF

Thermal EMF about 1 microvolt or less. 1 Form A, 2 Form A, 1 Form B & 1 Form C. 3, 5, 12 or 24 V coils. Suitable for data acquisition or thermocouple switching.

The Pickering Series 100 is a complete range of Single-in- Line (SIL) reed relays primarily intended for direct drive from 4000B CMOS or similar low current sources. They feature a very low level of thermal EMF.

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Series 101 – Low Thermal EMF

Thermal EMF Direct drive from 74HC or HCT. 1 Form A, 2 Form A, 1 Form B & 1 Form C. 3, 5, 12 or 24 V coils. Suitable for battery powered portable equipment.

The Series 101 have very high coil resistances. 5 Volt dry versions may be driven directly from 74HC or 74HCT logic without the need for additional drivers. 74HC logic will drive up to 4mA at 5 Volts, therefore a coil resistance of 1600 ohms is desirable to avoid running the IC at its maximum rating.

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Shop Reed Relays for Low Thermal EMF

The below table will help you narrow down our offering to get you the correct reed relay for your application.

Once you narrow your selections down you can download a reed relay data sheet for more information or request a quote to find out prices and lead times.

PEL Series
2
PEL Contact Configuration
Coil Voltage
Switching Current
(Amps)
Switching Power
(Watts)
PEL Diode
Switching Voltage
(DC/AC peak)
to GO
Stand-off Voltage
(DC/AC peak)
to GO
Width (mm)
to GO
Depth (mm)
to GO
Height (mm)
to GO
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PEL Series : Series 100
PEL Series : Series 101
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Part Number
Pickering Compare
Contact Configuration
Switching Current (Amps)
Switching Power (Watts)
Switching Voltage (DC or AC peak)
Stand-off Voltage (DC or AC peak)
Coil Voltage
Coil Resistance (Ω)
Switch Type
Diode
Depth (mm)
Width (mm)
Height (mm)
View Datasheet
Stock
Price
Add to Bag
1 Form B - SPST N.O.
0.5
Amps
10
200
220
5V
3000 Ω
General purpose
Yes
7.4
20.1
12.5
0 - MTO
$13.35
1 Form A - SPST N.O.
0.5
Amps
10
200
240
3V
1600 Ω
Low Level Dry Reed
No
7.4
20.1
9.4
0 - MTO
$9.42
1 Form C - SPDT Changeover
0.25
Amps
3
200
200
24V
6000 Ω
Changeover
No
7.4
20.1
9.4
0 - MTO
$15.13
1 Form A - SPST N.O.
0.5
Amps
10
500
1500
12V
6000 Ω
High Voltage Reed
Yes
7.4
20.1
9.4
0 - MTO
$14.77
2 Form A - DPST N.O.
1
Amps
20
200
240
24V
6000 Ω
General Dry Reed
Yes
7.4
20.1
12.5
5
$14.43
Max: 5
Min: 1
Step: 1
Add
2 Form A - DPST N.O.
2
Amps
50
500
550
5V
150 Ω
Std Mercury Reed
No
7.4
20.1
12.5
0 - MTO
$122.59
1 Form A - SPST N.O.
2
Amps
50
500
550
5V
375 Ω
Position Insensitive Hg
No
7.4
20.1
9.4
4
$65.27
1220
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