Test equipment oscilloscopes · 190M family

Fluke Biomedical 190M-4: troubleshooting and error codes

The ServiceForge knowledge base holds 10 documented symptoms for the Fluke Biomedical 190M-4, with 21 ranked causes, 15 diagnostic checks with test points and expected values, and 20 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

ST command returns non-zero status

The STATUS QUERY command (ST) returns an error status word indicating CPL interface errors. Each bit in the 16-bit status word represents a specific error condition.

Ranked causes

1. Illegal Command (bit 0) (common)
2. Data format of parameter is wrong (bit 1) (common)
3. Parameter out of range (bit 2) (common)
4. Invalid command in this CPL interface (bit 3) (occasional)
5. Command not implemented (bit 4) (occasional)
6. Invalid number of parameters (bit 5) (common)
7. Wrong number of data bits (bit 6) (occasional)
8. Conflicting instrument settings (bit 9) (rare)
9. Checksum error (bit 14) (rare)

First check

Send ST command and read status value

Test point: CPL interface
Expected: Status word 0 to 32767

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Query measurement command returns unexpected error code

QM or QM <no> command fails with non-zero acknowledge response

Ranked causes

1. Syntax Error (ACK=1) (common)
2. Execution Error (ACK=2) (common)
3. Synchronization Error (ACK=3) (occasional)
4. Communication Error (ACK=4) (occasional)

First check

Send QM command and read acknowledge

Test point: RS232 port
Expected: ACK = 0

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Any single invalid reading blocks entire query response

QM Syntax 2 returns no data when one or more requested measurement numbers are non-valid

Ranked causes

1. One or more requested measurement numbers invalid or inactive (common)

First check

Use QM Syntax 1 to identify valid measurements

Test point: ScopeMeter response
Expected: <valid>=1 for each measurement to query

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Communication Error acknowledge (ACK=4)

The ScopeMeter returns acknowledge code 4 indicating a communication error on the CPL interface.

Ranked causes

1. Serial communication line problem or baud rate mismatch (common)

First check

Verify serial port parameters

Test point: COM port
Expected: 1200, N, 8, 1 baud rate and protocol

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Execution Error acknowledge (ACK=2)

The ScopeMeter returns acknowledge code 2 indicating an execution error processing the command.

Ranked causes

1. Command cannot be executed in current instrument state (occasional)

First check

Verify instrument is ready to execute command

Test point: Instrument state
Expected: Instrument in valid state for command execution

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Maximum reading limit error on query

QM command with more than 10 measurement numbers returns error or partial data

Ranked causes

1. Query command exceeds 10 reading limit (common)

First check

Count measurement numbers in QM command

Test point: Command parameter list
Expected: 10 or fewer <no> values comma-separated

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Query measurement returns non-valid reading

QM Syntax 1 returns <valid>=0 or measurement data unavailable for selection

Ranked causes

1. Measurement reading not currently valid on instrument (common)

First check

Verify measurement is active and valid on display

Test point: ScopeMeter display screen
Expected: Measurement reading displayed with valid value

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Remote measurement query returns no data

QM command issued but no measurement readings returned from ScopeMeter

Ranked causes

1. No active measurements displayed on instrument screen (common)

First check

Verify active readings visible on ScopeMeter screen

Test point: ScopeMeter display
Expected: At least one measurement reading displayed

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Synchronization Error acknowledge (ACK=3)

The ScopeMeter returns acknowledge code 3 indicating a synchronization error in the communication protocol.

Ranked causes

1. Command and response timing out of synchronization (occasional)

First check

Verify acknowledge/response timing sequence

Test point: CPL interface handshake
Expected: Acknowledge received before status data

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Syntax Error acknowledge (ACK=1)

The ScopeMeter returns acknowledge code 1 indicating a syntax error in the sent command.

Ranked causes

1. Command format does not match specification (common)

First check

Review command string for syntax errors

Test point: Command buffer
Expected: Command must end with <cr> and match specified format

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Error codes

Code	Meaning	Trigger	Severity
`0`	No Error	Normal operation after command or query execution	info
`1`	Syntax Error	Invalid command syntax sent to instrument	error
`2`	Execution Error	Requested measurement number invalid for instrument model/firmware or reading is non-valid	error
`3`	Synchronization Error	Command sequence out of order or timing violation	error
`4`	Communication Error	RS232 serial link failure or configuration mismatch	error
`Status bit 0`	Illegal command	Invalid command sent to instrument	error
`Status bit 1`	Wrong parameter data format	Parameter sent with incorrect data type or format	error
`Status bit 10`	User Request (URQ)	Device-dependent user request event	unknown
`Status bit 11`	Flash ROM not programmable	Flash memory write protection or hardware failure	error
`Status bit 12`	Wrong programming voltage	Invalid voltage applied during flash programming	error
`Status bit 13`	Invalid keystring	Security keystring authentication failed	error
`Status bit 14`	Checksum error	Data integrity check failed	error
`Status bit 2`	Parameter out of range	Parameter value exceeds valid limits	warning
`Status bit 3`	Command not valid in present state	Command issued when instrument is in incompatible state	error
`Status bit 4`	Command not implemented	Command not available in this instrument model	error
`Status bit 5`	Invalid number of parameters	Wrong number of parameters in command	error
`Status bit 6`	Wrong number of data bits	Data field has incorrect bit count	error
`Status bit 7`	Flash ROM not present	Firmware memory module missing or not detected	critical
`Status bit 8`	Invalid flash software	Firmware checksum failed or corrupted	critical
`Status bit 9`	Conflicting instrument settings	Settings incompatible with current operation	warning

Likely causes and actions for each code are in ServiceForge. Connect ServiceForge to your AI

Community

0 fixes logged by technicians through their AI, with outcomes, for this model.

ServiceForge knowledge base record. Field-unverified unless technicians confirmed it. A teaching summary of the record, not a service manual. Export 2026-10-14.