Bosch Professional · India buying guide

Bosch GMS 120-27 vs D-tect 120 vs D-tect 200 C

Choose a wall scanner around the material you need to locate and the wall you are investigating. The GMS 120-27 covers metal, live-wire indication and wooden studs in drywall. The D-tect 120 adds radar-based detection of water-filled plastic pipes and non-live cables. The D-tect 200 C adds more wall settings, object-depth information in suitable views, empty-pipe detection under specific conditions, and saved measurement images. [1], [2], [3]

The headline 120 mm or 200 mm depth is a maximum for specific targets and conditions. It is not a universal scanning distance or an allowable drilling depth.

Read this before relying on a scan

An empty display, a green light or the absence of a live-wire warning does not prove that a wall is clear or that a cable is de-energised. Bosch warns that wall construction, moisture, interference and the objects themselves can affect detection. Check additional information such as construction plans and photographs before drilling, sawing or routing. Switch off loads and ensure that cables are de-energised before work; the scanner's classification is not an electrical isolation test. If the route or electrical status is uncertain, stop and obtain competent on-site verification. [4], [5], [6]

Live-wire classification has stricter conditions than general object detection. All three manuals specify a maximum relative humidity of 50% for their live/power-cable classification. A metal or non-metal object indication is not a guarantee of the object's identity. The model-specific cautions below still apply when a signal appears convincing. [4], [5], [6]

Bosch Professional GMS 120-27 product image

Wall scanners

GMS 120-27

For metal, live-wire indication and wooden studs in drywall.

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Bosch Professional D-tect 120 product image

Wall scanners

D-tect 120

Radar detection of water-filled plastic pipes and non-live cables.

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Bosch Professional D-tect 200 C product image

Wall scanners

D-tect 200 C

More wall settings, depth information in Object View and saved measurement images.

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Product images are illustrative. Check the product page for supplied accessories.

Understand detection depth

  • Detection depth is a conditional maximum for a particular object and substrate. Size, material, wall condition and mode can reduce it.
  • Magnetic metal includes reinforcing steel. Non-magnetic metal includes copper. A model's rating for one cannot automatically be applied to the other.
  • Object detection means the instrument has found a response consistent with an object. Material identification is a separate interpretation of that response. Neither establishes that drilling is safe.
  • Object-centre accuracy concerns how closely the indicated sideways position matches the actual position. Depth accuracy concerns how closely the indicated depth matches the actual depth. They are separate measurements.
  • Wall setting configures the scanner for the substrate. A view changes the presentation and can also impose a lower depth limit.

[4], [5], [6]

Compare detection and features

Depths below are conditional maxima. Object size, material, wall conditions and the selected mode can reduce detection depth.

Target or feature GMS 120-27 D-tect 120 D-tect 200 C
Bosch radar technology No Yes Yes
Ferrous metal 100 mm for 12 mm reinforcing steel 120 mm for metal in Concrete mode 200 mm for metal in dry concrete; select the appropriate depth and view
Non-ferrous metal 120 mm for a 15 mm copper pipe Copper detection; confirm suitability for the required depth with Bosch Copper detection; confirm suitability for the required depth with Bosch
Live wires or cable targets 50 mm for live 100–230 V wires; live classification has further limits Cable detection and live-wire indication; confirm suitability for the required depth with Bosch Up to 80 mm for live cables; wall conditions and live-classification limits apply
Wooden beams in drywall Wooden substructures in drywall; confirm suitability for the required depth with Bosch 38 mm 38 mm
Water-filled plastic pipes Do not choose it for plastic-pipe detection; wood search can misclassify other objects 60 mm in Concrete mode 80 mm for other objects in dry concrete; pipe diameter at least 10 mm; wall/view conditions apply
Empty plastic pipes Do not choose it for empty-plastic-pipe detection Do not choose it for empty-plastic-pipe detection; normally not detected in Drywall mode At least 20 mm diameter in solid surrounding material; not detected in Drywall or Panel Heating settings
Object-centre accuracy — ±10 mm, subject to conditions ±5 mm, subject to conditions
Object depth and records — — Object View has depth information and screenshot saving; USB-C or microSD transfer

Sources: [7]; [1] and [4]; [2] and [5]; [3] and [6].

For the D-tect 200 C, indicated-depth accuracy is ±5 mm in dry concrete and ±10 mm in early-age concrete. Its manual additionally requires allowance for ±0.5 mm per centimetre of object depth for objects deeper than 60 mm. The result also depends on the object, substrate and selected view. [6]

Choose the right wall mode

The D-tect 120 starts in Universal mode. Universal and Drywall modes have 60 mm maximum measuring depths, with wooden beams limited to 38 mm. Concrete mode allows up to 120 mm for ferrous metal and 60 mm for water-filled plastic pipes. These are conditional mode and target limits. Confirm copper and live-wire depth requirements with Bosch before choosing it for a depth-critical job. [5]

The D-tect 200 C provides these important distinctions:

  • Dry Concrete: up to 200 mm for ferrous metal and up to 80 mm for other objects. Confirm the required copper-detection depth with Bosch.
  • Early Age Concrete: metal up to 60 mm. Plastic pipes and cables may not be displayed, and live/non-live distinction is unavailable.
  • Horizontal Coring Brick: maximum 50 mm for the described flat-lying targets; cavities and empty plastic pipes may not appear.
  • Drywall: filled plastic pipes and wooden beams can look identical; empty plastic pipes are not recognised.
  • Panel Heating: intended for specified pipe and cable targets; empty plastic pipes are not displayed.
  • Spot View: maximum 60 mm and no depth information. Move the tool where possible; stationary detection of plastic pipes and timber is particularly limited.

The other wall settings are Brick/Universal and Vertical Coring Brick. Follow the conditions for each setting; selecting one does not establish that the wall is homogeneous or dry. [6]

GMS 120-27 for routine metal and drywall checks

Consider the GMS 120-27 for metal, live-wire indication and wooden substructures in drywall when you do not need saved measurement images. Its marking hole helps transfer a detected position to the wall. Wood search is an additional function; the tool searches for metal and live cables during each measurement. [1], [4]

Do use the intended grip, keep the sensor dry, maintain light and consistent contact, and scan across a suspected object's direction. Use crossing scans if the direction is unknown. After marking through the hole, start a new measurement because the pencil can affect the reading. For meshed reinforcement, follow the manual's preliminary circular scan, greater than 30 cm in diameter, then keep the tool on the substrate while starting the normal measurement. [4]

Don't enable wood search for every kind of wall. Bosch restricts it to drywall with a wooden substructure. Don't assume a non-metal indication is timber: water-filled plastic pipes, cables or gas lines can produce that indication. Do not continue using a visibly damaged or malfunctioning instrument. [4]

GMS 120-27 FAQs

Does 120 mm mean it finds every wire that deep?

No. The 120 mm manual value is for a 15 mm copper pipe. The stated maximum for live 100–230 V wires is 50 mm, with further detection conditions. [4]

Why can the live-wire symbol be absent?

The signal can be screened by metal, damp walls or conductive surfaces, and poor grounding can impair detection. Three-phase cables cannot be identified as live by this method because the phase signals cancel, although shallow metal detection may occur. An absent symbol does not establish a dead circuit. [4]

Can it find wooden studs behind any wall?

Use wood search only in drywall with a wooden substructure. Detection depth depends on the beam, plasterboard and wall conditions. If you need to find studs at a particular depth, confirm suitability with Bosch before buying. [4], [7]

Does it need calibration?

The tool is factory-calibrated. The manual describes recalibration for a persistent metal indication when no metal is nearby. This requires at least one-third battery charge and an object-free environment. Follow the complete procedure; if it does not restore operation, use an authorised Bosch service centre. Do not perform it as a routine step on every wall. [4]

Which battery does it use?

Two LR6 AA alkaline cells, two HR6 AA NiMH cells, or the specified BA 3.7V 1.0Ah A lithium-ion pack. The rechargeable pack is an accessory. Use the specified 3.7 V pack rather than a Bosch Professional GBA 12 V pack. [4]

D-tect 120 for radar scanning and three wall modes

Consider the D-tect 120 for plumbing, electrical or fitting work where water-filled plastic pipes and non-live cable detection are relevant, and the three wall modes cover the application. A detected-object indication can appear when the tool is placed on a narrow surface, but movement remains part of the prescribed measurement process. The manual specifies indoor use. [2], [5]

Do choose Universal, Concrete or Drywall deliberately. If the wall material is unknown, the manual says to begin with Universal. Keep light contact while moving; check the light, measuring indicator and orientation arrows together. Check the instrument before each use. [5]

Don't interpret a missing centre arrow as proof that there is no nearby object. Don't apply the 120 mm metal rating to water pipes or cables. Stop using the instrument if its response is abnormal, including a constant measurement indication in air or no response during the manual's pre-use check. [5]

D-tect 120 FAQs

Can it detect dry, empty PVC conduit?

Do not buy it on a general empty-conduit promise. The manual identifies water-filled plastic pipes as intended targets, says small empty pipes can remain undetectable in Universal mode, and says empty plastic pipes normally cannot be detected in Drywall mode. [5]

Does radar remove the live-wire limitations?

No. Metal screening, high water content and static effects can prevent or distort live-wire detection. General cable detection and live classification must be treated separately. [5]

How is it powered, and is a battery supplied?

It supports Bosch GBA 10.8 V/12 V packs or four LR6 AA alkaline cells in the designated adapter. Check whether a battery, adapter or charger is included before ordering. Match any replacement adapter to the exact scanner model. [5]

Can I use the full depth rating for copper and live wires?

Do not apply the headline 120 mm rating to every material. If your job depends on detecting copper or live wires at a specific depth, confirm suitability with Bosch before buying. Cable detection and live-wire classification have different limitations; neither proves a cable is de-energised. [5], [2], [7]

Is there a user calibration routine?

The operating and troubleshooting instructions do not provide a user calibration routine. Follow the pre-use checks, operating limits and service instructions in the manual. [5]

D-tect 200 C for more wall settings and saved results

Consider the D-tect 200 C when you need more wall-specific settings, depth information in Object View, or saved images for a work record. Empty-pipe detection depends on pipe size and the surrounding material. Object View offers the best measuring results and greatest depths described in the manual; Spot View is a restricted alternative for narrow areas. [6]

Do use the actual wall type and the appropriate view. In Object View, keep the wheels in contact, scan slowly in straight lines and cross the area in different directions. Bosch recommends a measuring path of at least 40 cm for optimum results; results begin after roughly 10 cm. Return over the path to refine a position before marking it. Confirm the installed software and the applicable instructions before relying on a feature described in the current manual. [6]

Don't read the drawing on the display as the object's exact physical width: thin objects may appear thicker and cylindrical objects narrower. Don't expect a deep object hidden behind a nearer one to be shown separately. Don't use Early Age Concrete mode to establish a cable's live/non-live state. [6]

D-tect 200 C FAQs

Is it a 200 mm scanner in every mode?

No. Spot View stops at 60 mm and does not provide depth information. Early Age Concrete has a 60 mm metal maximum, and horizontally perforated brick has a 50 mm maximum for the described targets. [6]

Does Leakage Detection prove a pipe leak?

It displays relative material moisture at the surface to help locate a possible leak. Different materials, shallow objects and joints can distort the response. It is not an absolute moisture-content reading or confirmation of a leak's cause. [6]

Does USB-C charge the battery?

No. The scanner's USB-C port is for data transfer to a PC. The manual explicitly excludes charging through that port. Use the correct external charger for a compatible rechargeable pack. [6]

Can I use any Bosch 12 V battery?

Use a Bosch GBA 10.8 V or GBA 12 V pack with a capacity of no more than 3 Ah. A 2.0 Ah pack is within that limit. These packs are not suitable for the GMS 120-27. [6]

Should I factory-reset it to calibrate it?

A factory reset restores menu options and permanently deletes saved images. The manual does not describe it as a calibration procedure. Follow the troubleshooting or service instructions for measurement problems. [6]

Power and accessories

Model Supported operating power Before you order
GMS 120-27 2 LR6 AA alkaline cells, 2 HR6 AA NiMH cells, or the BA 3.7V 1.0Ah A lithium-ion accessory Uses its own 3.7 V rechargeable accessory, not a GBA 12 V pack. Check whether batteries and a pouch are included.
D-tect 120 GBA 10.8/12 V pack or 4 AA alkaline cells with designated adapter AA cells require the designated adapter. Check whether an adapter, battery or charger is included.
D-tect 200 C GBA 10.8/12 V pack up to 3 Ah, or 4 AA alkaline cells with adapter AA cells require the designated adapter. Check whether an adapter, batteries, cable and pouch are included.

Check which batteries, adapters, chargers and accessories are included before ordering. Power options: [4], [5], [6]

Choosing accessories:

  • GMS 120-27: choose the specified Bosch BA 3.7V 1.0Ah A accessory. It is different from a GBA 12 V pack. [8], [4]
  • D-tect 120 and D-tect 200 C: a Bosch Professional GBA 12V 2.0Ah pack is a supported option. The D-tect 200 C has a 3 Ah capacity limit. Match the actual pack to the scanner before ordering. [9], [5], [6]
  • For GBA packs: the GAL 12V-40 is a Bosch Professional 12 V charger. Check the mains-input label and plug. It is not the charger for the GMS 120-27’s 3.7 V accessory. [10]
  • AA adapters: use the adapter specified for the exact scanner. The D-tect 200 C India variant lists AA1, order 1 608 M00 C1B. Do not assume that this part fits the D-tect 120 just because both use the AA1 name. Check whether an adapter is supplied before buying another. [3], [7]

Common questions and pre-use checklist

Which should I shortlist for fitting shelves in drywall?

Consider the GMS 120-27 if metal and wooden-stud location are your main requirements. The D-tect models add other target and display features. With every model, check what the detected object actually is and that the wall and fixing can support the load. [4], [5], [6]

Which should I shortlist for pipe-route investigations?

D-tect 120 supports water-filled plastic pipe detection. D-tect 200 C adds conditional empty-plastic-pipe detection and more wall settings. Neither promises a complete map of plumbing; layered walls, moisture, pipe size and the chosen mode can change the result. [5], [6]

Which is safest?

No scanner display can guarantee that a wall is clear or that a cable is de-energised. Choose the features your job needs, cross-check the wall and follow the appropriate electrical isolation process before penetrating work. [4], [5], [6]

Are the devices waterproof?

Keep all three scanners dry and follow their operating instructions. The GMS 120-27 is rated IP54. The D-tect 200 C is IP5X, with its lithium-ion battery and AA1 adapter excluded from that rating. Dust protection does not make a scanner suitable for wet use. [4], [5], [6]

Before a scan:

  1. Read the exact tool manual, confirm the tool's identity and inspect it for damage. Resolve unusual readings before use.
  2. Check plans and other available information. Identify the substrate and the target rather than choosing by the largest depth number.
  3. Keep the sensor dry, allow the tool to adjust after a large temperature change, use the intended grip and follow the grounding instructions. Avoid nearby sources of electromagnetic interference.
  4. Use the right wall mode and scanning movement. Review all indicators, repeat appropriate passes and cross-check ambiguous object identities.
  5. Before any penetrating work, ensure cables are de-energised through the appropriate electrical safety process. Do not use a scanner display as proof. Check the work afterwards as the manuals require.

This is a selection checklist, not a replacement for the complete operating instructions or site-specific safety arrangements. [4], [5], [6]

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See current prices, availability and supplied accessories on each product page. Both buttons open the product page and do not add an item to your cart automatically.

Use the current operating instructions that match your tool.

Compared using Bosch India specifications. Reviewed 11 October 2026.

Sources
  1. Bosch India GMS 120-27 (opens in a new tab)
  2. D-tect 120 (opens in a new tab)
  3. D-tect 200 C (opens in a new tab)
  4. GMS manual, pp8 and 17–18 (opens in a new tab)
  5. D-tect 120 manual, pp12–16 (opens in a new tab)
  6. D-tect 200 C manual, pp11 and 18–19 (opens in a new tab)
  7. 2026 India measuring catalogue, pp25–28 (opens in a new tab)
  8. Battery page (opens in a new tab)
  9. Battery page (opens in a new tab)
  10. Charger page (opens in a new tab)