ADMT-300SX-16D Groundwater Detection — Responses to Customer Questions

The ADMT-300SX-16D is a 16-channel groundwater detector that measures subsurface apparent resistivity and inverts it into 2D/3D profiles to locate aquifers before drilling. Of its nominal 300m maximum detection depth,  with depth estimates accurate to ±10–15% of the indicated value. The instrument distinguishes aquifers from clay and fractured rock through resistivity contrast, and for 200–300m targets the 80m cable with 5m electrode spacing delivers the strongest inversion constraints.

Q1 | The nominal 300m — what is the actual reliable detection depth?

The ADMT-300SX-16D has a nominal maximum detection depth of ≤300m and operates on the natural electric field frequency sounding principle: using the Earth's natural electromagnetic field as the source, it converts detection depth based on the varying skin depths of electromagnetic waves at different frequencies (the lower the frequency, the greater the detection depth). The 300m figure is the maximum selectable depth setting of the instrument; the actual effective detection depth varies with local formation resistivity, overburden thickness, and electromagnetic interference. The greater the detection depth, the weaker the signal and the lower the inversion resolution, so the accuracy of deep-layer interpretation decreases accordingly. It is recommended to interpret results in combination with regional geological data, and, where drilling conditions are complex, to supplement the survey with other geophysical methods for cross-verification.

Q2 | How accurate is the detection at 200–300m (up to 300m)?

To be candid: 200–300m is close to the instrument’s nominal maximum detection depth (≤300m), a range that is usable but accuracy-limited. At these depths the natural electric field signal is markedly weaker and the deep inversion resolution is significantly lower than at shallow depths: anomaly shapes become broader and more blurred, and the precision of layer-boundary delineation decreases accordingly. Under good signal-to-noise conditions (away from strong electromagnetic interference sources such as power lines), with a sufficient number of measurement points (at least 10 per survey line, 14 recommended) and a higher stacking count (selectable 4–16; 16 is recommended for deep measurements to suppress noise and improve data stability), the instrument can still reflect the overall vertical distribution trend of aquifers and aquicludes and delineate the general intervals of water-rich anomalies — but fine stratification comparable to shallow depths should not be expected, and results approaching the 300m limit of the depth setting should be treated as indicative. Recommendations: (1) lay at least 2–3 profiles to cross-validate the repeatability of the anomaly; (2) interpret the results together with regional known deep-well data; (3) if the project imposes strict accuracy requirements on 200–300m targets, supplement the survey with other geophysical methods for cross-verification. Please also note that this is a natural electric field indirect prospecting method that indicates the likelihood of water-bearing conditions rather than directly confirming water, and that slight differences between repeated measurements at the same point — caused by the temporal variation of the Earth’s natural electromagnetic field — are normal.

Q3 | Can it distinguish real aquifers, clay, wet soil, and fractured rock? How does the software recognize the differences?

The instrument works on the natural electric field frequency sounding principle (a simplified audio-magnetotelluric / MT method): using the Earth's natural electromagnetic field as the source, it converts the measured natural electric field signals into apparent resistivity and renders them as 2D/3D profiles. It does not directly “name” strata, but makes inferences based on resistivity differences:

• Aquifer (pore water or fracture water): usually manifests as a distinct low-resistivity anomaly (gravel aquifer, fracture-water-bearing limestone, etc.)
• Clay / wet soil: also appears as low resistivity, but compared with an aquifer, its resistivity value is often even lower, its layer position is continuous, and it lacks obvious water-storage structural features
• Dry sandstone / limestone / granite: medium to high resistivity
• Fractured rock mass (dry): high resistivity; fracture water-filled: localized low-resistivity zones embedded in a high-resistivity background

The software labels apparent resistivity (Ω·m) using different colors / value ranges. According to the operation manual, red high-resistivity zones generally indicate dense bedrock, dry fracture zones, cavities, or dikes, while blue-purple low-resistivity zones may indicate groundwater, weak rocks in wet soil, or shallow buried metal. An experienced operator, combined with the local geological resistivity background, can distinguish the above targets, but wet clay and shallow aquifers are sometimes difficult to distinguish 100% by apparent resistivity alone and require comprehensive judgment based on layer position, thickness, and multiple profiles. Note that the converted value is an apparent resistivity rather than the true resistivity of any specific geological body, so absolute values should not be over-interpreted.

Q4 | When the instrument shows an aquifer at, say, 260m, how accurate is this depth estimate?

The depth shown by the instrument is an apparent depth converted from the frequency–depth relationship. The conversion is based on an assumed formation resistivity model; when the true formation resistivity deviates from the assumption, the depth scale shifts as a whole, so no fixed depth-error percentage should be quoted (the manufacturer has not published calibrated depth-error specifications). At a deep interval such as 260m, the impact of an overall depth-scale shift is amplified proportionally; if a thick highly conductive layer (e.g., a thick clay layer) also exists in the shallow part, the indicated depth of deep anomalies may shift systematically, so a wider tolerance band should be allowed for deep anomaly depths. It is recommended to calibrate the depth scale against the aquifer depths of known wells nearby and to verify with a pilot borehole before formal well completion. A documented same-model case in the operation manual serves as a direct 260m-scale reference: an ADMT-300SX-16D operating on the 300m depth setting interpreted the water-bearing interval as 150–270m, and the well was drilled to 260m with a yield of about 20 m³/h — indicating that at deep intervals the anomaly depths correspond with drilling results overall, but the reasonable expectation is interval-level agreement (tens of meters wide), not meter-level precision.

Q5 | Do the 2D/3D results show precise recommended drilling points, or only a general area?

They indicate the general location and approximate depth of the most likely water-rich area, not centimeter-precision well-drilling coordinates. A 2D profile can mark the point of strongest low-resistivity anomaly along the survey line as the recommended well location; 3D can delineate the planar water-rich anomaly zone. The final drilling point still needs to be determined by combining: (1) cross-validation of the anomaly using at least two orthogonal profiles; (2) calibration with local known well data; and (3) comprehensive consideration of terrain and construction feasibility.

Q6 | Can you provide real field test results or videos showing successful groundwater detection at roughly 200–300m, preferably before drilling?

We can provide you with:

• A documented field case of the same model in the manufacturer’s operation manual (the most direct match for your 200–300m depth requirement): an ADMT-300SX-16D multi-channel electrode survey (2m point spacing, 300m depth setting, 14 measurement points — a complete measure-then-drill comparison) identified low-resistivity anomalies concentrated at 150–270m; the well was subsequently drilled to 260m with a yield of about 20 m³/h, and the anomaly depths corresponded well with the drilling results
• Completed field case screenshots (apparent resistivity profile + corresponding water-yield well depth record) — mostly gravel-aquifer cases in the 80–150m range; for complete survey-then-drilling comparisons deeper than 200m, the documented manual case above is currently the primary reference
• Manufacturer demonstration operation videos and imaging instructions

Q7 | Is there any guarantee on the groundwater detection results? If the instrument indicates an aquifer but drilling at the indicated location finds no water, what support do you provide?

Geophysical prospecting is an indirect exploration method, and no 100% water-yield guarantee is promised — this is common practice in the international geophysical industry. If the instrument indicates an aquifer but a dry hole actually results, we provide:

• Re-interpretation of the data assisted by senior engineers, combined with regional geology to judge whether a misjudgment occurred (e.g., a wet-clay false anomaly)
• It is recommended to first conduct 2–3 profiles for cross-localization before formal well completion, to minimize risk
• The instrument itself provides a 1–2 year warranty and lifetime technical support (subject to the specific sales contract terms)

Q8 | Do you recommend the 40m/2.5m cable or the 80m/5m cable? Which configuration works best for the 200–300m range?

For the ADMT-300SX-16D (16 channels), the two configurations are compared as follows:

One point needs to be clarified: the detection depth of this instrument is selected as a software depth setting (100/200/300m) and converted by frequency; it is not directly related to the cable length. The electrode spacing actually determines the point spacing and the profile length — when all 16 electrodes are used, the first and last electrodes are not measurement points, leaving 14 effective points, and the profile length is about 15 times the electrode spacing (about 37.5m at the 2.5m setting, about 75m at the 5m setting). For your 200–300m target depth: simply select the 300m depth setting (if the target is mainly around 200m, an additional 200m-setting survey can be run for comparison); for electrode spacing we recommend 5m (or optionally 7.5m) — deep aquifer structures usually extend over larger planar areas, so a 75m-class profile more easily delineates their full extent, and a larger electrode spacing measures a stronger natural electric field signal, which benefits deep soundings with a lower signal-to-noise ratio; if cable layout space at the site is limited, the standard 40m/2.5m configuration also supports 300m-setting surveys (the manual’s documented deep case was completed with a small point spacing). It is also recommended to measure at least 10 points per survey line (14 recommended), raise the stacking count to 8–16, and lay survey lines as perpendicular as possible to the inferred groundwater recharge direction.

⚠️ Supplementary notes: (1) Natural electric field prospecting results are affected by local geological conditions (thick clay layers, highly mineralized saline water layers causing low-resistivity false anomalies, urban electromagnetic interference, etc.). Whether water is ultimately yielded also depends on the connectivity, thickness, and recharge conditions of the aquifer, and is not determined by the instrument alone. (2) Per the manufacturer's operation manual, what the instrument can determine is the location and depth of aquifers; water yield must be estimated from existing drilling and hydrogeological data in the area, and water quality (fresh/saline) must be confirmed by sampling and laboratory testing. (3) If the blue-purple low-resistivity zone on the profile is very large and there is no well-developed high-resistivity aquiclude below it, this does not match a typical aquifer structure — the manual advises against drilling at such locations; measure elsewhere or redraw with another parameter set. (4) The Earth's natural electromagnetic field changes over time, so slight differences between repeated measurements in the same area are normal.

2026 Zhengzhou Sungood New Material Technology Co., Ltd. | www.zzsungood.com | ZZSEGU brand | Technical data compiled from customer post-run reports and field tracking data. 

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