SEAWARD 00 Series High Accuracy Resistance Decade Boxes Instruction Manual

High Accuracy Resistance
Decade Boxes
Type 00 Series
5, 6 & 8 Decades
Operating Instructions

Bracken Hill, South West Industrial Estate,
Peterlee, Co. Durham SR8 2SW. England.
Tel: +44 (0)191 586 3511
www.seaward.com
sales@seaward.com

Series High Accuracy Resistance Decade Boxes

Limited Warranty & Limitation of Liability
CROPICO guarantees this product for a period of 1 year. The period of warranty will be effective at the day of delivery.
© Copyright 2015
All rights reserved. Nothing from this edition may be multiplied, or made public in any form or manner, either electronically, mechanically, by photocopying, recording, or in any manner, without prior written consent from CROPICO. This also applies to accompanying drawings and diagrams.
Due to a policy of continuous development CROPICO reserves the right to alter the equipment specification and description outlined in this publication without prior notice and no part of this publication shall be deemed to be part of any contract for the equipment unless specifically referred to as an inclusion within such contract.
Disposal of Old Product
This product has been designed and manufactured with high quality materials and components that can be recycled and reused.
When the crossed out wheelie bin symbol is attached to a product it means the product is covered by the European Directive 2012/19/EU.
Please familiarise yourself with the appropriate local separate collection system for electrical and electronic products.
Please dispose of this product according to local regulations.
Do not dispose of this product along with normal waste material. The correct disposal of this product will help prevent potential negative consequences for the environment and human health.
Do not connect the decade box to voltage sources exceeding 30V AC or 60V DC!
User Note:
These Operating Instructions are intended for the use of Competent Personnel.

HIGH ACCURACY RESISTANCE DECADE BOXES 5, 6 & 8 DECADES

The 00# series of resistance boxes are available in 5, 6 & 8 decades. High Accuracy and wide range 0.001 ohm to 11 Megohms are combined in a compact lightweight case. The switches have gold plated contacts to ensure a low contact resistance and negligible thermal emf. Some models are particularly suited to Pt100 simulation with resolution as low as 0.001 ohm (±0.0025°C).
The Switches
Contact material gold plated brass. Contact Resistance <5mΩ. Insulation Resistance (all paths >10GΩ)
Resistance Coils
Temperature Co-efficient.
±3ppm/+20°C to +85°C. ±5ppm maximum over -55°C to +125°C. 0.1, 0.01 and 0.001 dials 10ppm/°C
Full Load Stability
±35ppm/10,000 hours. ±50ppm/26,000 Hours
No Load Stability
±25ppm/10,000 hours. ±35ppm/26,000 hours over full temperature range; -55°C to 125°C
Power Rating
0.33 watt (+85°C). 0.25 watt (+110°C)
Maximum Continuous Working
Voltage 30Vac or 60Vdc
Noise
Essentially non-measurable
Thermal EMF
<0.4μV/°C typical <1.5μV/°C max
Encapsulation
Moulded Epoxy
Leads
22 SWG tinned copper
Windings
Exclusive ‘air cushion’ technique provides virtually stressless elements for improved performance. Non inductively wound.
Direction of winding reversed at half turns point
7 Modesl to choose from

Model| Decades| Total
R 52| Smallest Steps 52| Residual  Resistance
---|---|---|---|---
005-B| 5| 1,112.10| 0.01| 1.0
006-A| 6| 01,112.| 0.001| 1.0
006-B| 6| 11,112.10| 0.01| 1.0
006-C| 6| 111,111| 0.1| 0.07
008-A| 8| 111,112.| 0.001| 1.0
008-B| 8| 1,111,112.| 0.01| 1.0
008-C| 8| 11,111,111| 0.1| 0.08

Accuracy of Decades

The 00# series of decade resistance boxes has been designed to be lightweight, small size, and require the minimum maintenance. The switches should not require any maintenance during their lifetime. The resistance elements are factory adjusted to be within specification and it is not possible to alter their value. In the event of a resistor becoming damaged it is necessary to replace the whole resistor. The 00# series of decade resistance boxes has been designed to be lightweight, small size, and require the minimum maintenance. The switches should not require any maintenance during their lifetime. The resistance elements are factory adjusted to be within specification and it is not possible to alter their value. In the event of a resistor becoming damaged it is necessary to replace the whole resistor.
Residual Resistance
With all the decade dials set at 0 there will be a resistance measured at the terminals, this resistance is made up form 2 components. The resistance of the wires connecting the decade switches to the terminals; this is a constant value. The contact resistance of the decade switches, this will vary each time the switch is turned or disturbed. This residual resistance must be added to the decade values set on the decades, it is therefore important that this residual should be as low and constant as possible. The CROPICO decade boxes have a low and stable residual resistance per decade. This value is controlled by the use of special low resistance switches.
It is not practical to manufacture decade resistance boxes where the lowest decade is less than 0.1Ω, to switch in steps of 0.01Ω and lower, special techniques need to be employed.
Low Value Decades
When switching decade resistance of 0.01Ω and lower the switch contact resistance variations become significant, this variation can be typically 40mΩ for an 8 decade unit and 30mΩ for a 6 decade and would, therefore, add greatly to the errors of the selected values. In addition the total residual resistance which would also include the internal wiring of the decade box could be significantly higher than the lowest decade values. CROPICO overcome this problem by using the Wagner Wolf decade, this technique enables
higher resistance values to be used for the decade which are then shunted to give the correct incremental steps. The residual value of the unit is deliberately increased to 1Ω, and the 1Ω decade will start at 1 and not zero. This is not normally a problem, because the applications that require values to be selected with high resolution would have a much greater full scale resistance, typical applications include the simulation of Pt100 temperatures. The Pt100 resistance thermometers have a resistance of 100Ω at 0°C and 0.01°C is approximately equal to 0.001Ω.

Note: the residual value of the decade resistance box must always be added to the value selected and this will give additional errors to these values, this emphasises the importance of the CROPICO low and more importantly stable residual resistance value.

Operation

To select a resistance value turn the dial of the appropriate decade until the desired value is indicated in the viewing window. The multiplier for each decade is shown below the dial i.e. x 0.1 or x 10 etc.
Example to select 121,234.5 Ω

Connection

The connections to the resistance box are made via the two 4mm terminals marked with the resistance symbol either banana plugs or spade terminals may be used. The third terminal marked with an earth symbol is connected directly to the top panel and case.

For Technical Support: www.seaward.com/support
For Service and Calibration Contact:
Service Department
Seaward Group
Unit 11
Bracken Hill
South West Industrial Estate
Peterlee
Co Durham
SR8 2LS
England
Tel: +44 (0) 191 587 8739
E-mail: service@seaward.com
CROPICO is a division of
Additional Products From Cropico
DIGITAL OHMMETERS
RESISTANCE DECADE BOXES
RESISTANCE STANDARDS
INSULATION TEST SETS
UNIVERSAL CALIBRATORS
HIPOT TESTERS
ELECTRICAL SAFETY TESTERS

Telephone, fax or e-mail for further information on the
above or for a copy of our general catalogue:
Tel: +44 (0) 191 586 3511
E-mail: sales@seaward.com
Website: www.seaward.com

References

• Electrical Safety Test Equipment Manufacturers | Seaward
• Services & support | FAQs, guides, webinars & more | Seaward

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