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MC Miller High Impedance Adapter #5615

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When structure-to-soil readings are taken across highly resistive materials such as dry soil, sand, rock, and concrete, readings can appear lower than their actual values. Relying on such low readings can lead to overcompensation of the rectifier's output, overprotection of the structure, and wasted resources.

No longer is it necessary to rely on the fixed 10 MΩ input impedance of standard voltmeters and data loggers for dependable readings. The solution to this common difficulty is the Selectable High Impedance Adapter. The adapter enables any standard impedance voltmeter or data logger to vary its input impedance, thereby eliminating contact resistance errors from readings.

General Information:

Due to the limitations of standard voltmeters, an error can be realized while performing readings with high impedance sources (e.g., structure-to-soil readings at the point where a copper/copper sulfate reference electrode makes contact with the earth). This error is a result of a current loop created by the voltmeter, which causes a drop across the source resistance. The Selectable High Impedance Adapter varies this current loop, allowing the user to determine when the error has been made insignificant. However, with higher impedance there is an increase in noise pickup. Therefore, when two adjacent ranges give the same readings, select the lower of the two ranges to limit pickup while maintaining the most precise reading.

The Selectable High Impedance Adapter is a multipurpose device used to vary the input impedance of data loggers and voltmeters, as well as a filter to remove AC noise.

The high impedance adapter has excellent AC noise rejection capabilities that improve as the frequency of the noise increases. Noise at a frequency of 50 Hz and 6.36 Vrms (9 V peak) produces only 1 count of error (+1.5mV) at the output, while at 60 Hz, it takes 19.1 VRMS (27 V peak of noise) to cause 1 count of error.

The selectable input impedance feature permits detection of high resistance in the external circuit and the elimination of resulting errors in virtually all cases. This feature is implemented by first taking the reading with the High Impedance Adapter in the 10 MΩ position to decrease the impedance, which will reduce any noise pickup and will result in the most precise reading.

In addition to giving precise readings, the High Impedance Adapter can also withstand a constant DC input of 700 volts as well as 1.5 kV voltage spikes.

The OFF position of the adapter functions as a means of testing its internal battery from a digital multimeter. To test the battery, turn the switch to the OFF/BAT TEST position and connect the High Impedance Adapter's output to a digital multimeter and set to the 200 mV range. A reading below 80 mV requires that the battery be changed.

· Improves accuracy of P/S readings

· Compensates for high resistance contacts between soil and electrode

· Detects high contact resistance at the test lead/structure connection

· Operates with any voltmeter

· Switch-selectable input impedance of 10, 25, 50, 100 and 200 MΩ

· Superior filtering of AC noise

· Watertight enclosure

· Small and convenient

Definitions:

Rejection is defined as the 60 Hz (50 Hz) RMS voltage required to cause the corresponding counts of ripple. Setting Time is defined as the time for the output to be within the corresponding counts of ripple for each rejection. Counts of Ripple refers to the amount of amplitude variation due to AC noise.

Specifications:

·       AC Noise (rms):  25.5 V, 34.0 V

·       DC Response and Accuracy:  It takes the High Impedance Adpater less than 200 ms to reach an output voltage of 2 VDC +1 mV with a 2 VDC input.  Maximum operational DC input:  +4 volts.

·       DC Voltage Input Impedance:  10, 25, 50, 100, 200 MΩ

·       Battery:  9 V alkaline, 9 V lithium

·       Battery Life Alkaline:  > 60 h

·       Battery Life Lithium:  > 210 h

·       Minimum Battery Voltage:  8.0 V

·       Operating Temperature:  -40 to +85°C, -40 to 185°F

·       Overall Size:  3-1/4 x 3-9/16 x 2-3/16 in

·       Box Size:  3-1/4 x 3-3/16 x 2-3/16 in

·       Weight:  9.3 oz

·       Option:  Mounting plate for attaching the Selectable High Impedance Adapter to MC Miller Co.'s.

Frequency Response

·       Frequency:  50 Hz, 60 Hz

·       50 Hz Attenuation:  -74.3 dB

·       60 Hz Attenuation:  -85.6 dB

·       50 Hz Counts of Error:  1 in 5210

·       60 Hz Counts of Error:  1 in 19149

AC Rejection at 50 Hz

·       Rejection (rms):  6.36 V, 11.3 V, 17.7 V

·       Counts of Ripple at 6.36 Vrms:  1 (+1.5 mV)

·       Counts of Ripple at 11.3 Vrms:  2 (+2.5 mV)

·       Counts of Ripple at 17.7 Vrms:  3 (+3.5 mV)

·       Settling Time at 6.36 Vrms:  < 200 ms

·       Settling Time at 11.3 Vrms:  < 200 ms

·       Settling Time at 17.7 Vrms:  < 200 ms

 

Product(s)

Item #Product NameQuoteSpecs
Cat #5615 MC Miller Selectable High Impedance Adapter #5615 PDF

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